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Sex Determination

There are 2 types of sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria chromosomes Chromosomes In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. DNA Types and Structure in humans: X and Y. Chromosomal sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria is male when a Y chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics is present (e.g., 46,XY or 47, XXY XXY Klinefelter syndrome is a chromosomal aneuploidy characterized by the presence of 1 or more extra X chromosomes in a male karyotype, most commonly leading to karyotype 47,XXY. Klinefelter syndrome is associated with decreased levels of testosterone and is the most common cause of congenital hypogonadism. Klinefelter Syndrome) and female when the Y chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics is absent (e.g., 46,XX or 45,X0). Male phenotypes develop when a specific gene Gene A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Basic Terms of Genetics, called the SRY gene Gene A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Basic Terms of Genetics (usually found on the Y chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics), is present, stimulating differentiation of the gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types into testes Testes Gonadal Hormones. The testes Testes Gonadal Hormones then produce testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens (triggering development of the penis Penis The penis is the male organ of copulation and micturition. The organ is composed of a root, body, and glans. The root is attached to the pubic bone by the crura penis. The body consists of the 2 parallel corpora cavernosa and the corpus spongiosum. The glans is ensheathed by the prepuce or foreskin. Penis: Anatomy and scrotum Scrotum A cutaneous pouch of skin containing the testicles and spermatic cords. Testicles: Anatomy externally and the ejaculatory system internally) and antimüllerian hormone ( AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea), which causes regression Regression Corneal Abrasions, Erosion, and Ulcers of the müllerian ducts. Without the SRY gene Gene A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Basic Terms of Genetics, ovaries Ovaries Ovaries are the paired gonads of the female reproductive system that contain haploid gametes known as oocytes. The ovaries are located intraperitoneally in the pelvis, just posterior to the broad ligament, and are connected to the pelvic sidewall and to the uterus by ligaments. These organs function to secrete hormones (estrogen and progesterone) and to produce the female germ cells (oocytes). Ovaries: Anatomy develop; without testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens, external female genitalia develop; and without AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea, the müllerian ducts persist and differentiate into the fallopian tubes Fallopian tubes The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The fallopian tubes receive an ovum after ovulation and help move it and/or a fertilized embryo toward the uterus via ciliated cells lining the tubes and peristaltic movements of its smooth muscle. Uterus, Cervix, and Fallopian Tubes: Anatomy, uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Uterus, Cervix, and Fallopian Tubes: Anatomy, and upper vagina Vagina The vagina is the female genital canal, extending from the vulva externally to the cervix uteri internally. The structures have sexual, reproductive, and urinary functions and a rich blood supply, mainly arising from the internal iliac artery. Vagina, Vulva, and Pelvic Floor: Anatomy.

Last updated: 30 Jun, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Overview

Definitions

The following definitions are relevant to the understanding Understanding Decision-making Capacity and Legal Competence of normal sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria development:

  • Chromosomal sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria (also referred to as genetic sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria): the sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria as defined by a person’s chromosomes Chromosomes In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. DNA Types and Structure:
    • Males: include a Y chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics, typically 46,XY
    • Females: do not include a Y chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics, typically 46,XX 
  • Gonadal sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria: describes the type of gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types present within an individual
    • Males: testes Testes Gonadal Hormones
    • Females: ovaries Ovaries Ovaries are the paired gonads of the female reproductive system that contain haploid gametes known as oocytes. The ovaries are located intraperitoneally in the pelvis, just posterior to the broad ligament, and are connected to the pelvic sidewall and to the uterus by ligaments. These organs function to secrete hormones (estrogen and progesterone) and to produce the female germ cells (oocytes). Ovaries: Anatomy
    • Hermaphroditic gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types: ovotestis
  • Phenotypic sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria: the appearance of the external genitalia (starting at birth) and secondary sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria characteristics (at puberty Puberty Puberty is a complex series of physical, psychosocial, and cognitive transitions usually experienced by adolescents (11-19 years of age). Puberty is marked by a growth in stature and the development of secondary sexual characteristics, achievement of fertility, and changes in most body systems. Puberty)
  • Sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria determination: The process of transformation Transformation Change brought about to an organism’s genetic composition by unidirectional transfer (transfection; transduction, genetic; conjugation, genetic, etc.) and incorporation of foreign DNA into prokaryotic or eukaryotic cells by recombination of part or all of that DNA into the cell’s genome. Bacteriology of the indifferent gonad into a testis or an ovary
  • Sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria differentiation: Development of the phenotype Phenotype The complete genetic complement contained in the DNA of a set of chromosomes in a human. The length of the human genome is about 3 billion base pairs. Basic Terms of Genetics as an expression of hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types produced by the specific gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types
  • Gender Gender Gender Dysphoria ( sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria) assignment: Designation of male or female gender Gender Gender Dysphoria at birth
  • Gender identity Gender identity A person’s concept of self as being male and masculine or female and feminine, or ambivalent, based in part on physical characteristics, parental responses, and psychological and social pressures. It is the internal experience of gender role. Sexual Physiology: the sense of self as being male or female
  • Sexual orientation Sexual orientation The sexual functions, activities, attitudes, and orientations of an individual. Sexuality, male or female, becomes evident at puberty under the influence of gonadal steroids (testosterone or estradiol), and social effects. Sexual Physiology: Refers to the target of sexual arousal and is independent of the person’s gender identity Gender identity A person’s concept of self as being male and masculine or female and feminine, or ambivalent, based in part on physical characteristics, parental responses, and psychological and social pressures. It is the internal experience of gender role. Sexual Physiology

Overview of typical sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria development

  • Chromosomal sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria → determines gonadal sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria → determines phenotypic sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria
  • Up until 6 weeks of gestation, sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria development is identical and nonbinary; developing structures include:
  • The genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure present at fertilization Fertilization To undergo fertilization, the sperm enters the uterus, travels towards the ampulla of the fallopian tube, and encounters the oocyte. The zona pellucida (the outer layer of the oocyte) deteriorates along with the zygote, which travels towards the uterus and eventually forms a blastocyst, allowing for implantation to occur. Fertilization and First Week will determine how the developing bipotent gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types differentiate (e.g., into a testis or an ovary)
  • The developing gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types will then secrete hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types.
    • The presence and/or absence of specific hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types will determine how the remaining structures differentiate.
    • In general, female organs and structures are the “default” phenotype Phenotype The complete genetic complement contained in the DNA of a set of chromosomes in a human. The length of the human genome is about 3 billion base pairs. Basic Terms of Genetics if specific genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure and hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types are not present to stimulate male differentiation.
  • Internal and external genital structures develop in response to hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types in utero.
  • Secondary sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria characteristics develop in response to hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types at puberty Puberty Puberty is a complex series of physical, psychosocial, and cognitive transitions usually experienced by adolescents (11-19 years of age). Puberty is marked by a growth in stature and the development of secondary sexual characteristics, achievement of fertility, and changes in most body systems. Puberty.

Overview of genital structures

  • Gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types: develop based on the karyotype Karyotype The full set of chromosomes presented as a systematized array of metaphase chromosomes from a photomicrograph of a single cell nucleus arranged in pairs in descending order of size and according to the position of the centromere. Congenital Malformations of the Female Reproductive System/ genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure present
    • Testes Testes Gonadal Hormones
      • Develop when sex-determining region of the Y chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics (SRY gene Gene A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Basic Terms of Genetics) is present
      • Secrete testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens and antimüllerian hormone ( AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea)
    • Ovaries Ovaries Ovaries are the paired gonads of the female reproductive system that contain haploid gametes known as oocytes. The ovaries are located intraperitoneally in the pelvis, just posterior to the broad ligament, and are connected to the pelvic sidewall and to the uterus by ligaments. These organs function to secrete hormones (estrogen and progesterone) and to produce the female germ cells (oocytes). Ovaries: Anatomy: develop when the SRY gene Gene A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Basic Terms of Genetics is absent 
    • Ovotestis: a gonad containing both ovarian and testicular tissue found in individuals with true hermaphroditism True hermaphroditism True hermaphroditism, or ovotesticular disorder of sexual development (ODSD), is characterized by the presence of an ovotesticular gonad that contains both ovarian and testicular elements. Individuals are usually born with ambiguous genitalia, but the diagnosis is rarely confirmed before puberty. The most common karyotype is 46,XX, and less often, 46,XY can be identified. True Hermaphroditism
  • Wolffian structures Wolffian structures Congenital Disorders of Sexual Development: differentiate from the wolffian (mesonephric) ducts in the presence of testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens:
    • Epididymis Epididymis The convoluted cordlike structure attached to the posterior of the testis. Epididymis consists of the head (caput), the body (corpus), and the tail (cauda). A network of ducts leaving the testis joins into a common epididymal tubule proper which provides the transport, storage, and maturation of spermatozoa. Testicles: Anatomy
    • Vas deferens Vas Deferens The excretory duct of the testes that carries spermatozoa. It rises from the scrotum and joins the seminal vesicles to form the ejaculatory duct. Testicles: Anatomy
    • Seminal vesicles Seminal vesicles A saclike, glandular diverticulum on each ductus deferens in male vertebrates. It is united with the excretory duct and serves for temporary storage of semen.
    • Ejaculatory ducts Ejaculatory Ducts Paired ducts in the human male through which semen is ejaculated into the urethra.
  • Müllerian structures Müllerian structures Congenital Disorders of Sexual Development: differentiate from the müllerian (paramesonephric) ducts when AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea is absent:
    • Uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Uterus, Cervix, and Fallopian Tubes: Anatomy
    • Fallopian tubes Fallopian tubes The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The fallopian tubes receive an ovum after ovulation and help move it and/or a fertilized embryo toward the uterus via ciliated cells lining the tubes and peristaltic movements of its smooth muscle. Uterus, Cervix, and Fallopian Tubes: Anatomy
    • Upper vagina Vagina The vagina is the female genital canal, extending from the vulva externally to the cervix uteri internally. The structures have sexual, reproductive, and urinary functions and a rich blood supply, mainly arising from the internal iliac artery. Vagina, Vulva, and Pelvic Floor: Anatomy
  • External genitalia: develop from undifferentiated genital tubercle Genital Tubercle Development of the Urogenital System, genital swelling Swelling Inflammation, and genital folds Genital folds Development of the Urogenital System based on the presence or absence of testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens
    • Male: testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens 
      • Penis Penis The penis is the male organ of copulation and micturition. The organ is composed of a root, body, and glans. The root is attached to the pubic bone by the crura penis. The body consists of the 2 parallel corpora cavernosa and the corpus spongiosum. The glans is ensheathed by the prepuce or foreskin. Penis: Anatomy 
      • Scrotum Scrotum A cutaneous pouch of skin containing the testicles and spermatic cords. Testicles: Anatomy
    • Female: lack of testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens

Secondary sexual characteristics Secondary Sexual Characteristics Precocious Puberty

Secondary sexual characteristics Secondary Sexual Characteristics Precocious Puberty develop based on the hormonal milieu at puberty Puberty Puberty is a complex series of physical, psychosocial, and cognitive transitions usually experienced by adolescents (11-19 years of age). Puberty is marked by a growth in stature and the development of secondary sexual characteristics, achievement of fertility, and changes in most body systems. Puberty.

  • Androgenic characteristics Androgenic characteristics Congenital Disorders of Sexual Development (i.e., “male”): due to the presence of testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens and/or dihydrotestosterone Dihydrotestosterone A potent androgenic metabolite of testosterone. It is produced by the action of the enzyme 3-oxo-5-alpha-steroid 4-dehydrogenase. Gonadal Hormones ( DHT DHT A potent androgenic metabolite of testosterone. It is produced by the action of the enzyme 3-oxo-5-alpha-steroid 4-dehydrogenase. Gonadal Hormones):
    • Pubic and axillary hair
    • Facial and body hair in an androgenic distribution and quality Quality Activities and programs intended to assure or improve the quality of care in either a defined medical setting or a program. The concept includes the assessment or evaluation of the quality of care; identification of problems or shortcomings in the delivery of care; designing activities to overcome these deficiencies; and follow-up monitoring to ensure effectiveness of corrective steps. Quality Measurement and Improvement (dark and coarse)
    • Deepening of the voice
    • ↑ Muscle mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast
  • Estrogenic characteristics Estrogenic characteristics Congenital Disorders of Sexual Development (i.e., “female”): due to the presence of estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries: Anatomy
    • Breast development
    • Wider hips

The Sex Chromosomes

There are 2 sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria chromosomes Chromosomes In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. DNA Types and Structure in humans: X and Y.

Y chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics

  • Approximately 58 million base pairs
  • Estimated to have 70–200 genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure 
  • Acrocentric chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics 
  • The Y chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics is quintessentially the “sex-determining” chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics   
    • Contains the SRY gene Gene A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Basic Terms of Genetics, which is key for male development
    • Y-linked traits are inherited from male to male only 
  • Pairs with the X chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics during cell division Cell Division A type of cell nucleus division by means of which the two daughter nuclei normally receive identical complements of the number of chromosomes of the somatic cells of the species. Cell Cycle
  • Pseudoautosomal region: 
    • An area on the short arm Arm The arm, or “upper arm” in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm: Anatomy of the Y chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics that is homologous to a region on the short arm Arm The arm, or “upper arm” in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm: Anatomy of the X chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics
    • Some crossing over Crossing over The reciprocal exchange of segments at corresponding positions along pairs of homologous chromosomes by symmetrical breakage and crosswise rejoining forming cross-over sites (holliday junctions) that are resolved during chromosome segregation. Crossing-over typically occurs during meiosis but it may also occur in the absence of meiosis, for example, with bacterial chromosomes, organelle chromosomes, or somatic cell nuclear chromosomes. Basic Terms of Genetics between the X and Y chromosomes Chromosomes In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. DNA Types and Structure is possible at this location.
A male set of chromosomes

A male set of chromosomes Chromosomes In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. DNA Types and Structure:
The Y chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics is highlighted.

Image: “Human male karyotpe high resolution – Chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics Y” by National Human Genome Genome The complete genetic complement contained in the DNA of a set of chromosomes in a human. The length of the human genome is about 3 billion base pairs. Basic Terms of Genetics Research Research Critical and exhaustive investigation or experimentation, having for its aim the discovery of new facts and their correct interpretation, the revision of accepted conclusions, theories, or laws in the light of newly discovered facts, or the practical application of such new or revised conclusions, theories, or laws. Conflict of Interest Institute. License: Public Domain

X chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics

  • Approximately 155 million base pairs
  • Estimated to have 800–900 genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure 
  • Genetic disorders caused by mutations in genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure on the X chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics:
    • Called X-linked X-linked Genetic diseases that are linked to gene mutations on the X chromosome in humans or the X chromosome in other species. Included here are animal models of human X-linked diseases. Common Variable Immunodeficiency (CVID) disorders
    • May be inherited in a dominant or recessive fashion
    • More often affect Affect The feeling-tone accompaniment of an idea or mental representation. It is the most direct psychic derivative of instinct and the psychic representative of the various bodily changes by means of which instincts manifest themselves. Psychiatric Assessment males, who have only 1 copy of the X chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics
  • X-inactivation:
    • Also called lyonization
    • All X chromosomes Chromosomes In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. DNA Types and Structure except 1 are inactivated early in embryologic development in females:
      • In individuals with a 46,XX genotype Genotype The genetic constitution of the individual, comprising the alleles present at each genetic locus. Basic Terms of Genetics, 1 X chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics will be inactivated.
      • In individuals with a 47, XXY XXY Klinefelter syndrome is a chromosomal aneuploidy characterized by the presence of 1 or more extra X chromosomes in a male karyotype, most commonly leading to karyotype 47,XXY. Klinefelter syndrome is associated with decreased levels of testosterone and is the most common cause of congenital hypogonadism. Klinefelter Syndrome genotype Genotype The genetic constitution of the individual, comprising the alleles present at each genetic locus. Basic Terms of Genetics, 2 X chromosomes Chromosomes In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. DNA Types and Structure will be inactivated.
    • The inactivated chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics is compacted into heterochromatin Heterochromatin The portion of chromosome material that remains condensed and is transcriptionally inactive during interphase. DNA Types and Structure, creating a structure known as a Barr body Barr body In the interphase nucleus, a condensed mass of chromatin representing an inactivated X chromosome. Each X chromosome, in excess of one, forms sex chromatin (Barr body) in the mammalian nucleus. Basic Terms of Genetics.
    • Partially responsible for the phenomenon known as dosage Dosage Dosage Calculation compensation Compensation Respiratory Acidosis, which is the reason why aneuploidies of the sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria chromosomes Chromosomes In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. DNA Types and Structure have substantially smaller impacts on an individual than autosomal aneuploidies.
  • X chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics aneuploidy is one of the most common chromosomal abnormalities.

The Genetics of Sex Determination

Typical male development

  • Male development starts because of the presence of the sex-determining region of the Y chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics gene Gene A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Basic Terms of Genetics (SRY gene Gene A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Basic Terms of Genetics)
    • Located on the short arm Arm The arm, or “upper arm” in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm: Anatomy of the Y chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics at Yp11.3
    • Produces a transcription factor Transcription factor Generic term for proteins necessary for transcription Regulation of Transcription called testis-determining factor (TDF), which is also known as the SRY protein SRY protein Development of the Urogenital System 
  • TDF:
    • Alters the expression of multiple transcription factors Transcription Factors Endogenous substances, usually proteins, which are effective in the initiation, stimulation, or termination of the genetic transcription process. Stages of Transcription, which trigger Trigger The type of signal that initiates the inspiratory phase by the ventilator Invasive Mechanical Ventilation the differentiation of structures unique to the testes Testes Gonadal Hormones:
      • Sertoli cells Sertoli Cells Supporting cells projecting inward from the basement membrane of seminiferous tubules. They surround and nourish the developing male germ cells and secrete androgen-binding protein and hormones such as anti-mullerian hormone. The tight junctions of sertoli cells with the spermatogonia and spermatocytes provide a blood-testis barrier. Testicles: Anatomy
      • Leydig cells Leydig Cells Steroid-producing cells in the interstitial tissue of the testis. They are under the regulation of pituitary hormones; luteinizing hormone; or interstitial cell-stimulating hormone. Testosterone is the major androgen (androgens) produced. Testicles: Anatomy
      • Seminiferous tubules Seminiferous Tubules The convoluted tubules in the testis where sperm are produced (spermatogenesis) and conveyed to the rete testis. Spermatogenic tubules are composed of developing germ cells and the supporting sertoli cells. Testicles: Anatomy
    • Suppresses the expression of genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure required for ovarian development:
      • Wnt4
      • R spondin 1 (Rspo1)
  • Sertoli cells Sertoli Cells Supporting cells projecting inward from the basement membrane of seminiferous tubules. They surround and nourish the developing male germ cells and secrete androgen-binding protein and hormones such as anti-mullerian hormone. The tight junctions of sertoli cells with the spermatogonia and spermatocytes provide a blood-testis barrier. Testicles: Anatomy secrete AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea
    • Also called müllerian-inhibiting substance Müllerian-inhibiting substance A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea (MIS) or müllerian-inhibiting factor (MIF)
    • AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea causes regression Regression Corneal Abrasions, Erosion, and Ulcers of paramesonephric (i.e., müllerian) ducts.
    • Without AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea, the paramesonephric ducts Paramesonephric ducts A pair of ducts near the wolffian ducts in a developing embryo. In the male embryo, they degenerate with the appearance of testicular anti-mullerian hormone. In the absence of anti-mullerian hormone, mullerian ducts give rise to the female reproductive tract, including the oviducts; uterus; cervix; and vagina. Development of the Urogenital System would differentiate into female structures (the fallopian tubes Fallopian tubes The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The fallopian tubes receive an ovum after ovulation and help move it and/or a fertilized embryo toward the uterus via ciliated cells lining the tubes and peristaltic movements of its smooth muscle. Uterus, Cervix, and Fallopian Tubes: Anatomy, uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Uterus, Cervix, and Fallopian Tubes: Anatomy, and upper vagina Vagina The vagina is the female genital canal, extending from the vulva externally to the cervix uteri internally. The structures have sexual, reproductive, and urinary functions and a rich blood supply, mainly arising from the internal iliac artery. Vagina, Vulva, and Pelvic Floor: Anatomy).
  • Leydig cells Leydig Cells Steroid-producing cells in the interstitial tissue of the testis. They are under the regulation of pituitary hormones; luteinizing hormone; or interstitial cell-stimulating hormone. Testosterone is the major androgen (androgens) produced. Testicles: Anatomy secrete testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens:
    • Stimulate differentiation of the wolffian/mesonephric ducts into:
      • Epididymis Epididymis The convoluted cordlike structure attached to the posterior of the testis. Epididymis consists of the head (caput), the body (corpus), and the tail (cauda). A network of ducts leaving the testis joins into a common epididymal tubule proper which provides the transport, storage, and maturation of spermatozoa. Testicles: Anatomy
      • Vas deferens Vas Deferens The excretory duct of the testes that carries spermatozoa. It rises from the scrotum and joins the seminal vesicles to form the ejaculatory duct. Testicles: Anatomy
      • Seminal vesicles Seminal vesicles A saclike, glandular diverticulum on each ductus deferens in male vertebrates. It is united with the excretory duct and serves for temporary storage of semen.
      • Ejaculatory ducts Ejaculatory Ducts Paired ducts in the human male through which semen is ejaculated into the urethra.
    • Converted to DHT DHT A potent androgenic metabolite of testosterone. It is produced by the action of the enzyme 3-oxo-5-alpha-steroid 4-dehydrogenase. Gonadal Hormones by 5α-reductase → stimulates development of:
      • The prostate Prostate The prostate is a gland in the male reproductive system. The gland surrounds the bladder neck and a portion of the urethra. The prostate is an exocrine gland that produces a weakly acidic secretion, which accounts for roughly 20% of the seminal fluid. from the urogenital sinus Urogenital Sinus Congenital Malformations of the Female Reproductive System 
      • External male genitalia: penis Penis The penis is the male organ of copulation and micturition. The organ is composed of a root, body, and glans. The root is attached to the pubic bone by the crura penis. The body consists of the 2 parallel corpora cavernosa and the corpus spongiosum. The glans is ensheathed by the prepuce or foreskin. Penis: Anatomy and scrotum Scrotum A cutaneous pouch of skin containing the testicles and spermatic cords. Testicles: Anatomy
  • Key genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure/ proteins Proteins Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein. Energy Homeostasis involved in the testicular differentiation:
    • SRY gene Gene A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Basic Terms of Genetics/TDF: 
      • Up-regulates an autosomal gene Gene A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Basic Terms of Genetics called SOX9
      • Suppresses the expression of genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure required for ovarian development
    • SOX9:
      • Induces morphologic changes that are critical in the differentiation of Sertoli cells Sertoli Cells Supporting cells projecting inward from the basement membrane of seminiferous tubules. They surround and nourish the developing male germ cells and secrete androgen-binding protein and hormones such as anti-mullerian hormone. The tight junctions of sertoli cells with the spermatogonia and spermatocytes provide a blood-testis barrier. Testicles: Anatomy and seminiferous tubules Seminiferous Tubules The convoluted tubules in the testis where sperm are produced (spermatogenesis) and conveyed to the rete testis. Spermatogenic tubules are composed of developing germ cells and the supporting sertoli cells. Testicles: Anatomy from precursor cells
      • Binds the promoter region of the AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea gene Gene A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Basic Terms of Genetics → produces AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea
      • Along with TDF, SOX9 is considered essential for testes Testes Gonadal Hormones development
    • Steroidogenic factor 1 (SF1): works with SOX9 at the promoter region of the AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea gene Gene A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Basic Terms of Genetics to ↑ production of AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea in Sertoli cells Sertoli Cells Supporting cells projecting inward from the basement membrane of seminiferous tubules. They surround and nourish the developing male germ cells and secrete androgen-binding protein and hormones such as anti-mullerian hormone. The tight junctions of sertoli cells with the spermatogonia and spermatocytes provide a blood-testis barrier. Testicles: Anatomy
    • WT1: transcription factor Transcription factor Generic term for proteins necessary for transcription Regulation of Transcription that works with SF-1 to further ↑ production of AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea
    • Desert hedgehog (DHH): produced in Sertoli cells Sertoli Cells Supporting cells projecting inward from the basement membrane of seminiferous tubules. They surround and nourish the developing male germ cells and secrete androgen-binding protein and hormones such as anti-mullerian hormone. The tight junctions of sertoli cells with the spermatogonia and spermatocytes provide a blood-testis barrier. Testicles: Anatomy to help stimulate the differentiation of Leydig cells Leydig Cells Steroid-producing cells in the interstitial tissue of the testis. They are under the regulation of pituitary hormones; luteinizing hormone; or interstitial cell-stimulating hormone. Testosterone is the major androgen (androgens) produced. Testicles: Anatomy
    • Dosage-sensitive sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria reversal, adrenal hypoplasia Adrenal Hypoplasia Hypoaldosteronism critical region, on chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics X, gene Gene A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Basic Terms of Genetics 1 (DAX1): 
      • Represses SF1 → ↓ AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea production 
      • Located on the short arm Arm The arm, or “upper arm” in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm: Anatomy of the X chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics

Typical female development

Differentiation and development of the müllerian ducts and external genitalia will proceed when testicular androgens Androgens Androgens are naturally occurring steroid hormones responsible for development and maintenance of the male sex characteristics, including penile, scrotal, and clitoral growth, development of sexual hair, deepening of the voice, and musculoskeletal growth. Androgens and Antiandrogens and AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea are absent.

  • Development of the ovary from the bipotent gonad requires absence of SRY (preventing differentiation into testes Testes Gonadal Hormones).
  • Other key genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure/ proteins Proteins Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein. Energy Homeostasis involved in female sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria determination:
    • Autosomal genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure that repress SOX9:
      • Wnt4
      • Rspo1
      • FOXL2
    • DAX1 
  • Without SOX9 and with DAX1:
    • AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea production allows for the müllerian ducts to persist and develop.
    • No Leydig cells Leydig Cells Steroid-producing cells in the interstitial tissue of the testis. They are under the regulation of pituitary hormones; luteinizing hormone; or interstitial cell-stimulating hormone. Testosterone is the major androgen (androgens) produced. Testicles: Anatomy → no testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens → female external genitalia develop
  • Embryos develop in the “female hormonal environment” within their mother, so it is unclear whether hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types produced by the fetus are required for their embryologic development.
  • At puberty Puberty Puberty is a complex series of physical, psychosocial, and cognitive transitions usually experienced by adolescents (11-19 years of age). Puberty is marked by a growth in stature and the development of secondary sexual characteristics, achievement of fertility, and changes in most body systems. Puberty, estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries: Anatomy stimulates:
    • Breast development
    • Widening of the hips
Sex determination in humans

Sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria determination in humans:
The Y chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics includes the SRY gene SRY gene The primary testis-determining gene in mammalians, located on the Y chromosome. It codes for a high mobility group box transcription factor (transcription factors) which initiates the development of the testes from the embryonic gonads. Development of the Urogenital System (Sex-determining Region Y) that codes for testis-determining factor (TDF), causing embryonic gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types to form into testes Testes Gonadal Hormones (male gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types) and lead to male development.
In the absence of the TDF protein (i.e., no Y chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics), the embryonic gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types develop into ovaries Ovaries Ovaries are the paired gonads of the female reproductive system that contain haploid gametes known as oocytes. The ovaries are located intraperitoneally in the pelvis, just posterior to the broad ligament, and are connected to the pelvic sidewall and to the uterus by ligaments. These organs function to secrete hormones (estrogen and progesterone) and to produce the female germ cells (oocytes). Ovaries: Anatomy (female gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types).
Females possess 2 copies of the X chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics (XX);
males possess 1 X and 1 Y (shorter) chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics (XY).

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Clinical Relevance: Disorders of Sexual Development

  • Disorders of sexual development (DSDs) are a group of conditions characterized by atypical sexual development in an individual, which may involve abnormalities in the structure and/or function of the internal reproductive organs and/or external genitalia. 
  • Congenital adrenal hyperplasia Congenital adrenal hyperplasia Congenital adrenal hyperplasia (CAH) consists of a group of autosomal recessive disorders that cause a deficiency of an enzyme needed in cortisol, aldosterone, and androgen synthesis. The most common subform of CAH is 21-hydroxylase deficiency, followed by 11β-hydroxylase deficiency. Congenital Adrenal Hyperplasia: Increased formation of male sexual hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types ( androgens Androgens Androgens are naturally occurring steroid hormones responsible for development and maintenance of the male sex characteristics, including penile, scrotal, and clitoral growth, development of sexual hair, deepening of the voice, and musculoskeletal growth. Androgens and Antiandrogens) with virilization of the external female genitals. Characterized by low levels of cortisol Cortisol Glucocorticoids, high levels of ACTH, and adrenal hyperplasia Hyperplasia An increase in the number of cells in a tissue or organ without tumor formation. It differs from hypertrophy, which is an increase in bulk without an increase in the number of cells. Cellular Adaptation.
  • Androgen insensitivity syndrome Androgen insensitivity syndrome Androgen insensitivity syndrome (AIS) is an X-linked recessive condition in which a genetic mutation affects the function of androgen receptors, resulting in complete (CAIS), partial (PAIS), or mild (MAIS) resistance to testosterone. All individuals with AIS have a 46,XY karyotype; however, phenotypes vary and include phenotypic female, virilized female, undervirilized male, and phenotypic male individuals. Androgen Insensitivity Syndrome ( AIS AIS Scoliosis): Mutations in the androgen receptors Receptors Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors cause partial or complete resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing to testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens. Genotypically, affected individuals have a 46,XY karyotype Karyotype The full set of chromosomes presented as a systematized array of metaphase chromosomes from a photomicrograph of a single cell nucleus arranged in pairs in descending order of size and according to the position of the centromere. Congenital Malformations of the Female Reproductive System and testes Testes Gonadal Hormones present internally. Testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens levels are elevated, and some of this testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens is converted to estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries: Anatomy peripherally. Clinically, individuals with complete AIS Complete AIS Androgen Insensitivity Syndrome will present with no sexual hair and have normal-appearing external female genitalia. Individuals are usually assigned female gender Gender Gender Dysphoria at birth and will present at puberty Puberty Puberty is a complex series of physical, psychosocial, and cognitive transitions usually experienced by adolescents (11-19 years of age). Puberty is marked by a growth in stature and the development of secondary sexual characteristics, achievement of fertility, and changes in most body systems. Puberty with amenorrhea Amenorrhea Absence of menstruation. Congenital Malformations of the Female Reproductive System.
  • Aromatase Aromatase An enzyme that catalyzes the desaturation (aromatization) of the ring a of C19 androgens and converts them to C18 estrogens. In this process, the 19-methyl is removed. This enzyme is membrane-bound, located in the endoplasmic reticulum of estrogen-producing cells of ovaries, placenta, testes, adipose, and brain tissues. Aromatase is encoded by the cyp19 gene, and functions in complex with NADPH-ferrihemoprotein reductase in the cytochrome p450 system. Adipose Tissue: Histology deficiency: results in an inability to convert testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens to estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries: Anatomy, primarily causing virilization of the external genitalia in females.
  • 5α-reductase deficiency: autosomal recessive Autosomal recessive Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal recessive diseases are only expressed when 2 copies of the recessive allele are inherited. Autosomal Recessive and Autosomal Dominant Inheritance disorder that impairs conversion of testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens to DHT DHT A potent androgenic metabolite of testosterone. It is produced by the action of the enzyme 3-oxo-5-alpha-steroid 4-dehydrogenase. Gonadal Hormones, preventing full development of the external genitalia in males. This disorder results in ambiguous genitalia Ambiguous Genitalia Primary Amenorrhea in 46,XY individuals at birth. 
  • Pure gonadal dysgenesis Pure gonadal dysgenesis 46,XX gonadal dysgenesis is a disorder present in individuals who are phenotypic females with normal karyotypes of 46,XX and who have streak gonads with no functional ovarian tissue. It is also called “pure gonadal dysgenesis” to differentiate these patients from those who present with the phenotype of Turner’s syndrome. 46,XX Gonadal Dysgenesis: results in nonfunctional gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types. In 46,XX individuals, pure gonadal dysgenesis Pure gonadal dysgenesis 46,XX gonadal dysgenesis is a disorder present in individuals who are phenotypic females with normal karyotypes of 46,XX and who have streak gonads with no functional ovarian tissue. It is also called “pure gonadal dysgenesis” to differentiate these patients from those who present with the phenotype of Turner’s syndrome. 46,XX Gonadal Dysgenesis presents with premature Premature Childbirth before 37 weeks of pregnancy (259 days from the first day of the mother’s last menstrual period, or 245 days after fertilization). Necrotizing Enterocolitis ovarian insufficiency (i.e., premature Premature Childbirth before 37 weeks of pregnancy (259 days from the first day of the mother’s last menstrual period, or 245 days after fertilization). Necrotizing Enterocolitis menopause Menopause Menopause is a physiologic process in women characterized by the permanent cessation of menstruation that occurs after the loss of ovarian activity. Menopause can only be diagnosed retrospectively, after 12 months without menstrual bleeding. Menopause) in otherwise normal-appearing females. In 46,XY individuals, the condition is known as Swyer syndrome Swyer syndrome Swyer syndrome is a disorder of sex development caused by a defect in the SRY gene on chromosome Y. The syndrome is characterized by complete testicular dysgenesis in an individual who has a 46,XY karyotype and is phenotypically female. Swyer Syndrome; without functional testes Testes Gonadal Hormones, testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens and MIF are not produced, so individuals have external female genitalia and normal müllerian structures Müllerian structures Congenital Disorders of Sexual Development. Affected individuals present in adolescence with primary amenorrhea Primary Amenorrhea Primary amenorrhea is defined as the absence of menstruation in a girl by age 13 years in the absence of secondary sex characteristics or by the age of 15 years with the presence of secondary sex characteristics. Etiologies can originate in the hypothalamic-pituitary-ovarian (HPO) axis or from anatomic abnormalities in the uterus or vagina. Primary Amenorrhea and lack of all secondary sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria characteristics.  
  • Klinefelter syndrome Klinefelter syndrome Klinefelter syndrome is a chromosomal aneuploidy characterized by the presence of 1 or more extra X chromosomes in a male karyotype, most commonly leading to karyotype 47,XXY. Klinefelter syndrome is associated with decreased levels of testosterone and is the most common cause of congenital hypogonadism. Klinefelter Syndrome: Chromosomal aneuploidy characterized by the existence of ≥ 1 extra X chromosomes Chromosomes In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. DNA Types and Structure in a male karyotype Karyotype The full set of chromosomes presented as a systematized array of metaphase chromosomes from a photomicrograph of a single cell nucleus arranged in pairs in descending order of size and according to the position of the centromere. Congenital Malformations of the Female Reproductive System (e.g., 47, XXY XXY Klinefelter syndrome is a chromosomal aneuploidy characterized by the presence of 1 or more extra X chromosomes in a male karyotype, most commonly leading to karyotype 47,XXY. Klinefelter syndrome is associated with decreased levels of testosterone and is the most common cause of congenital hypogonadism. Klinefelter Syndrome or 48,XXXY). Symptoms are not usually observed during childhood. During adulthood, individuals are typically tall males who present with gynecomastia Gynecomastia Gynecomastia is a benign proliferation of male breast glandular ductal tissue, usually bilateral, caused by increased estrogen activity, decreased testosterone activity, or medications. The condition is common and physiological in neonates, adolescent boys, and elderly men. Gynecomastia and infertility Infertility Infertility is the inability to conceive in the context of regular intercourse. The most common causes of infertility in women are related to ovulatory dysfunction or tubal obstruction, whereas, in men, abnormal sperm is a common cause. Infertility related to hypogonadism Hypogonadism Hypogonadism is a condition characterized by reduced or no sex hormone production by the testes or ovaries. Hypogonadism can result from primary (hypergonadotropic) or secondary (hypogonadotropic) failure. Symptoms include infertility, increased risk of osteoporosis, erectile dysfunction, decreased libido, and regression (or absence) of secondary sexual characteristics. Hypogonadism. Educational difficulties are also common.
  • Turner syndrome Turner syndrome Turner syndrome is a genetic condition affecting women, in which 1 X chromosome is partly or completely missing. The classic result is the karyotype 45,XO with a female phenotype. Turner syndrome is associated with decreased sex hormone levels and is the most common cause of primary amenorrhea. Turner Syndrome: chromosomal aneuploidy characterized by the absence of an X chromosome Chromosome In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. Basic Terms of Genetics in a female karyotype Karyotype The full set of chromosomes presented as a systematized array of metaphase chromosomes from a photomicrograph of a single cell nucleus arranged in pairs in descending order of size and according to the position of the centromere. Congenital Malformations of the Female Reproductive System (e.g., 45,X0). Clinical manifestations include a characteristic phenotype Phenotype The complete genetic complement contained in the DNA of a set of chromosomes in a human. The length of the human genome is about 3 billion base pairs. Basic Terms of Genetics (short stature, webbed neck Webbed neck Turner Syndrome, widely spaced nipples) and multiple anomalies usually involving the cardiac, renal, reproductive, skeletal, and lymphatic systems. Gonadal dysgenesis Gonadal dysgenesis A number of syndromes with defective gonadal developments such as streak gonads and dysgenetic testes or ovaries. The spectrum of gonadal and sexual abnormalities is reflected in their varied sex chromosome (sex chromosomes) constitution as shown by the karyotypes of 45, X monosomy (Turner syndrome); 46, XX (gonadal dysgenesis, 46xx); 46, XY (gonadal dysgenesis, 46, xy); and sex chromosome mosaicism. Their phenotypes range from female, through ambiguous, to male. This concept includes gonadal agenesis. Wilms Tumor and infertility Infertility Infertility is the inability to conceive in the context of regular intercourse. The most common causes of infertility in women are related to ovulatory dysfunction or tubal obstruction, whereas, in men, abnormal sperm is a common cause. Infertility are likely.
  • True hermaphroditism True hermaphroditism True hermaphroditism, or ovotesticular disorder of sexual development (ODSD), is characterized by the presence of an ovotesticular gonad that contains both ovarian and testicular elements. Individuals are usually born with ambiguous genitalia, but the diagnosis is rarely confirmed before puberty. The most common karyotype is 46,XX, and less often, 46,XY can be identified. True Hermaphroditism: presence of an ovotesticular gonad that contains both ovarian and testicular elements. Affected individuals are usually born with ambiguous genitalia Ambiguous Genitalia Primary Amenorrhea, and the internal structures depend on the adjacent gonadal tissue. The most common karyotype Karyotype The full set of chromosomes presented as a systematized array of metaphase chromosomes from a photomicrograph of a single cell nucleus arranged in pairs in descending order of size and according to the position of the centromere. Congenital Malformations of the Female Reproductive System is 46,XX.

References

  1. Wilhelm, D., Palmer, S., & Koopman, P. (2007). Sex determination and gonadal development in mammals. Physiol Rev 87, pp. 1–28. https://doi.org/10.1152/physrev.00009.2006
  2. Bashamboo, A., & McElreavey, K. (2016). Mechanism of sex determination in humans: insights from disorders of sex development. Sex Dev 10, pp. 313–325. https://doi.org/10.1159/000452637
  3. Cotinot, C., Pailhoux, E., Jaubert, F., & Fellous, M. (2002). Molecular genetics of sex determination. Semin Reprod Med 20, pp. 157–168. https://doi.org/10.1055/s-2002-35380
  4. McClelland, K., Bowles, J., & Koopman, P. (2012). Male sex determination: insights into molecular mechanisms. Asian J Androl 14, pp. 164–171. https://doi.org/10.1038/aja.2011.169
  5. Hake, L., & O’Connor C. (2008). Genetic mechanisms of sex determination. Nature Education 1:25. https://www.nature.com/scitable/topicpage/genetic-mechanisms-of-sex-determination-314/ 
  6. Franco, H. L., & Yao, H. H. C. (2012). Sex and hedgehog: roles of genes in the hedgehog signaling pathway in mammalian sexual differentiation. Chromosome Res 20:247–258.  https://doi.org/10.1007/s10577-011-9254-z
  7. Hiort, O. (2021). Typical sex development. UpToDate. Retrieved October 15, 2021, from https://www.uptodate.com/contents/typical-sex-development 

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