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Autosomal Disorders and Genomic Imprinting

by Georgina Cornwall, PhD
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    I promised this in an earlier lecture. We’re going to now revisit genomic imprinting. Genomic imprinting can be fairly tough to understand. These are two conditions that we are certainly going to need to know about for the USMLE exams, Prader-Willi syndrome and Angelman's syndrome. Again, genomic imprinting occurs when the expression of a deletion is different depending on the parent of origin. So both these syndromes result from a microdeletion on chromosome 15. However, the expression is completely different dependent on which parent that chromosome was inherited from. Before we dive all the way into it, I wanted to take a quick review of the genomic imprinting scenario. We’ll review this. This figure should look pretty familiar. The parent of origin is the thing that we need to consider here. We’ll again start with the top of the figure. We’re showing an oocyte sort of on the central right hand side that has a pink chromosome in it. That chromosome is marked as being from the mother and has certain region on it that is imprinted, epigenetically modified so that certain region of that chromosome is not expressed. When that ovum is fertilized by a sperm, it is going to be fertilized by a sperm who also has a chromosome that has been marked as from the father, so from the sperm. It has a region that has also been epigenetically modified to mark it as non-expressed region of that chromosome. Both of these chromosomes will end up in the embryo. They are marked as paternally inherited or maternally inherited. Then those cells will continue to divide and an adult carries the same marked chromosomes. So, Is that clear? With those same marked chromosomes then, the adult will have germline cells which we see over here on the side...

    About the Lecture

    The lecture Autosomal Disorders and Genomic Imprinting by Georgina Cornwall, PhD is from the course Chromosomal Disorders.


    Included Quiz Questions

    1. An epigenetic phenomenon by which certain genes are expressed in a parent-of-origin-specific manner
    2. The process in which ribosomes in a cell's cytoplasm create proteins
    3. The process in which a particular segment of DNA is copied into RNA
    4. A regulated process that results in a single gene coding for multiple proteins
    5. The process in which a 5' cap and a 3' polyadenylation tail are added to a messenger RNA.
    1. imprints are erased and re-established through each generation.
    2. Imprinted genes of one generation remain imprinted in the next generation.
    3. Imprinting of genes is not normal and always leads to diseases.
    4. Genomic Imprinting is based on classic Mendelian inheritance.
    5. Epigenetic marks are imprinted in the somatic cells of an organism.
    1. The paternally inherited chromosome has a deletion in the PWS region while maternally inherited chromosome is hypermethylated.
    2. The paternally inherited chromosome has a deletion in the PWS region while maternally inherited chromosome is nonmethylated.
    3. The maternally inherited chromosome has a deletion in the PWS region while paternally inherited chromosome is hypermethylated.
    4. The maternally inherited chromosome has a deletion in the PWS region while paternally inherited chromosome is hypomethylated.
    5. Both chromosomes are maternally inherited and one has a deletion in PWS region.
    1. The maternally inherited chromosome has a deletion in the AS region while paternally inherited chromosome is hypermethylated.
    2. The paternally inherited chromosome has a deletion in the AS region while maternally inherited chromosome is nonmethylated.
    3. The paternally inherited chromosome has a deletion in the AS region while maternally inherited chromosome is hypermethylated.
    4. Both chromosomes are paternally inherited and one has a deletion in AS region.
    5. The maternally inherited chromosome has a deletion in the AS region while paternally inherited chromosome is nonmethylated.

    Author of lecture Autosomal Disorders and Genomic Imprinting

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD


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