One Gene One Polypeptide Hypothesis

by Georgina Cornwall, PhD

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    00:01 In this next sequence of lectures, we will be digging into gene expression and regulation of gene expression. What better place to start than by giving you an overview and introducing you to the genetic code? By the end of this lecture, you should be able to distinguish between transcription and translation as well as discuss the one gene one polypeptide hypothesis as well as list the roles of RNA in gene expression and describe what the genetic code is.

    00:33 Let us move into looking at the central dogma for gene expression. Important information comes from DNA and flows through RNA and eventually to protein. A short way to say this really is that we will take DNA and we will transcribe the message into messenger RNA and then we will translate that message into proteins or polypeptides. I have a little analogy here that sort of helps with why we do at this way, but the DNA let us say is the laptop and it is best to keep your laptop in the office, not the kitchen. I generally go to my laptop in my office and I will print out a copy of my recipe so that I don't spill stuff all over my laptop. I can use that recipe and I can translate it into some delicious food. The messenger RNA is okay. That is the copy. It can get messy. We don't though want to damage the DNA. Messenger RNA helps keep your computer clean, helps keep the original copy clean. DNA to RNA to protein works out great, but then we learned about the enzyme reverse transcriptase, which actually can make a copy of RNA and go back to DNA so that sort of puts a little bit of a hole in the central dogma, but we don't generally see reverse transcriptase. You will be introduced to it when we get into genomics and biotechnologies, DNA technologies. There is one hole, but it is not the end of the world. In general, the central dogma does apply. We also have a one gene one polypeptide hypothesis. It has been modified from a one gene one protein hypothesis because we know from looking at protein structure that you have often multiple subunits in a protein like we looked at hemoglobin. Two of those subunits are coded for by two different genes. One gene one polypeptide holds up pretty well although the proteins can be posttranslationally modified. You might have multiple outcomes from that one polypeptide chain. Insulin is a great example where we actually cut a piece out of the end polypeptide chain. I will tell you all about that in a future lecture also.

    03:16 In this sense, we have each gene coding for one enzyme. Now in prokaryotes, we often see that there is a cluster of genes with one origin for transcription and those genes will be transcribed in sequence to produce multiple enzymes involved in a similar process. For example, here we have an enzyme that is being coded for in a biochemical pathway where we change one precursor molecule using that enzyme and to another molecule using that enzyme into other molecule so on and so forth. Biochemical pathways are going to be managed by the enzymes that are produced in a gene sequence. Here two enzymes being produced in sequence to produce enzymes involved in a biochemical pathway that are related to each other. One gene one polypeptide lets us just know that. Now we will take a very brief look at transcription.

    About the Lecture

    The lecture One Gene One Polypeptide Hypothesis by Georgina Cornwall, PhD is from the course Gene Expression.

    Included Quiz Questions

    1. Proteins
    2. Nucleotides
    3. Amino acids
    1. Reverse transcriptase
    2. DNA polymerase
    3. RNA polymerase
    4. DNA ligase
    5. Helicase

    Author of lecture One Gene One Polypeptide Hypothesis

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD

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    Micro-Lecture lacks the expected concentration of information. Lecture isn't linear in nature or coherent.
    By Neuer N. on 01. July 2020 for One Gene One Polypeptide Hypothesis

    I suppose it depends on your learning style. That is, most of the medical students I've spoken to, appreciate concise and coherent lectures - Unfortunately, in my personal opinion, this micro-lecture lacked the fundamental high concentration of information that most of us are looking for - to take notes, and practice the spaced repetition model. Instead, her speaking pace, and vocal expression are slightly too fast and the way in which she attempts to outline a basic idea isn't linear in nature which leads the viewer wanting to know more, while simultaneously trying to ignore the off-topic rants. Note: Clearly, she's qualified to teach - however, valid of a point that may be, doesn't mean she has the practical communication skills to do so. Therefore, this is not a question of intelligence, rather - communication and linguistic expression. There will certainly people who prefer this method, I however, can not recommend.

    amazing teaching!
    By Debydgacha l. on 19. August 2019 for One Gene One Polypeptide Hypothesis

    she was understandable! i liked her! i am so prepared for the next test we will be doing

    By Jared C. on 02. August 2019 for One Gene One Polypeptide Hypothesis

    The professor did not do a good job explaining concepts clearly, went too fast, covered little material