Term
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Definition
| adds bases at random at the junction for the heavy chain; an additional source of genetic diversity in somatic recombination |
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Term
| activation induced cytidine deaminase (AID) |
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Definition
| the enzyme responsible for somatic hypermutation; isotype switching...it is the master regulator of secondary Ab diversification |
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Term
| what determines whether B cell will express membrane bound vs secreted Ab? |
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Definition
| variation in polydenylation site |
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Term
| the 12-23 bp rule for heptamers and nonamers |
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Definition
| these conserved regions serve as important signals to RAG 1, RAG2 enzymes for splicing in the somatic rearrangement process |
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Term
| what is the heavy chain of Ig homologous to on TCR? |
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Definition
| heavy chain ~ B chain: both have VDJ rearrangement |
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Term
| what is the light chain of Ig homologous to on TCR? |
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Definition
| light chain ~ alpha chain (TCR): VJ rearrange |
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Term
| recombination activating genes (RAG1, RAG2) |
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Definition
initiated on the heavy chain genes, specifically on the D (diversity) and Jh (joining, heavy) regions of both alleles
shuffle, separate, and reform the VDJ genes; RAG proteins initiate VDJ recombination
rearrangement occurs on both chromosomes independently |
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Term
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Definition
| necessary for activation and proliferation of lymphocytes in lymphoid organs; previously activated, mature lymphocytes go to lymph tissue to bind antigen and be stimulated to proliferate |
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Term
| what are the molecules associated with TCR signaling? |
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Definition
| CD3 subunits: gamma, delta, epsilon, zeta chains |
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Term
| unproductive recombination |
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Definition
| most of the rearrangements are outside of appropriate reading frames to produce a functional protein; about 2/3 attempts (cells) will be eliminated |
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Term
| what needs to occur before isotype switching is even an option? |
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Definition
| successful VDJ rearrangement that produces IgM can be induced to change the isotype to a different heavy chain; molecules produced by helper T cells can induce DNA rearrangement via switch recombination sites to result in Ab of a different isotype |
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