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Mediation of the Genetic Recombination – Lymphocyte Development

by Peter Delves, PhD
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    Let’s take a few moments to look in a little bit more detail at how this genetic recombination process actually is mediated. Really depends on two things, or requires two things. Requires a number of different enzymes that catalyze the recombination process, but it also requires recognition sequences for these enzymes, in other words substrates for these enzymes that are within the DNA sequence. Okay? They’re not in the part of the DNA that encodes the protein but they lie immediately adjacent to that part. And they’re called Recombination Signal Sequences or RSS. And the enzymes that recognize these Recombination Signal Sequences, their nucleotide sequences as I say, flanking the V, D and J segments; the enzymes that recognize, or the two most important enzymes that recognize these Recombination Signal Sequences are called RAG-1 and RAG-2. So heavy chain VDJ recombination, and likewise light chain VJ recombination is mediated by the recombinase enzymes RAG-1 and RAG-2; stands for Recombination Activating Genes, even though they’re actually proteins that come from those genes. And they recognize these Recombination Signal Sequences or RSS, which are nucleotides flanking the V, D and J gene segments. And as you can see from this particular picture, the V segment has an RSS immediately three prime or downstream of the protein coding sequence. The D segment has two RSSs, one either side. And the J segment has a signal RSS five prime or immediately upstream of its sequence. So following successful heavy chain recombination of VDJ, the light chain is then recombined, because an antibody needs both a heavy chain and a light chain. And here we can see the Variable region of the kappa (k) light chain, around about 40 different Variable segments for the light chain in the k… for the k light chain. And...

    About the Lecture

    The lecture Mediation of the Genetic Recombination – Lymphocyte Development by Peter Delves, PhD is from the course Adaptive Immune System. It contains the following chapters:

    • Mediation of the Genetic Recombination
    • Genetic Recombination of the Heavy Chain
    • Allelic Exclusion

    Included Quiz Questions

    1. 2
    2. 1
    3. 3
    4. 4
    5. 5
    1. They make sure that the RSS sequence is translated into protein
    2. They are recombinase enzymes that help mediate recombination of immunoglobulin gene
    3. They mediate both heavy and light chain recombination
    4. They recognize Recombination Signal Sequence (RSS) nucleotides
    5. They regulate the expression of the V, D, and J segments
    1. Two attempts at recombination of the heavy chain, two attempts at recombination of the kappa light chain, two attempts at recombination of lamda light chain
    2. Two attempts at recombination of the heavy chain, two attempts at recombination of lamda light chain, two attempts at recombination of the kappa light chain
    3. Two attempts at recombination of the heavy chain, one attempt at recombination of the kappa light chain, one attempt at recombination of lamda light chain
    4. Two attempts at recombination of the heavy chain, one attempt at recombination of lamda light chain, one attempt at recombination of the kappa light chain
    5. Two attempts at recombination of the kappa light chain, two attempts at recombination of lamda light chain, two attempts at recombination of the heavy chain
    1. A B cell that expresses different light and heavy chains on it's IgM and IgD
    2. Overexpression of light chains
    3. A B cell with more specificity for an antigen
    4. More variability on the hypervariable regions
    5. Increased IgM production

    Author of lecture Mediation of the Genetic Recombination – Lymphocyte Development

     Peter Delves, PhD

    Peter Delves, PhD


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