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Old 02-15-2011
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Arrow Test your knowledge #11! (Immunology)

A 22-year-old medical student requires a Tdap vaccination to fulfill the hospital requirements for her clinical rotations. The vaccine contains tetanus, diphtheria, and pertussis toxoids, and out of the millions of naive B cells with distinct, randomly generated antigen specificities in her body, there will be some that match the antigens in the vaccine with enough affinity to mount a humoral immune response and eventually result in the presence of memory B cells specific for those toxins. The group of enzymes responsible for the diversity of antigen receptors in immunoglobin are called:

A. Human leukocyte antigen (HLA)
B. Major histocompatibility complex (MHC)
C. heavy chain protein
D. T cell receptors (TCR)
E. VDJ recombinase
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  #2  
Old 02-15-2011
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Answer is E.

Q is asking for enzymes. the only choice is E. VDJ recombination is where we get millions and billions of diverse immunoglobulin molecules.
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the answer is E
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Arrow Watch this

http://www.dnatube.com/video/254/VDJ-Recombination
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E. VDJ recombinase
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Old 02-15-2011
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Correct Answer Correct!

Correct! The answer is E. VDJ recombinase.

Toward the end of lymphocyte differentiation, these enzymes bring the joining (J) and diversity (D, not found in light-chain genes) gene segments, which lie between the variable (V) and constant (C) regions, in close proximity to the V region and cleave the DNA, which is repaired by ligases. Between the cleaving and ligating, nucleotides get removed from the genes by exonucleases, others randomly added at recombination sites and uneven DNA ends filled out (these are mechanisms of junctional diversity), and the genes have been shuffled about or excluded from the final sequence (these are mechanisms of combinatorial diversity). This process happens in the genes for heavy and light chain immunoglobins as well as those encoding T cell receptors.

@drahmednawaz: good point about using the word "enzyme" - too much trying to teach in the stem can give away the answer! I should have been a little more vague, perhaps...
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