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15 Cards in this Set
- Front
- Back
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GOD in pre-Ag exposure occurs where?
post-Ag exposure? |
pre-Ag: Bone marrow
Post-Ag: peripheral lymphoid tissues |
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each Ig is encoded on how many chromosomes?
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3 separate gene complexes on 3 diff chromosomes: 1 complex each for lamdba light, kappa light, and heavy chains.
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how many gene segments are req for the variable region?
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2 segments for the variable region in the light chain (V,J)
3 segments for the variable region in the heavy chain (V,D,J) |
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what is a leader sequence?
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it comes before the V segment for each gene encoding for the variable region; it directs the protein after synthesis
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describe the formation of a lambda light chain? kappa light? heavy?
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lambda light: pick one V and one J/C complex travel together
kappa: pick 1 V, 1J. only 1 C available heavy: pick 1 V, 1D, 1J, followed by C(mu)and the rest of the C regions |
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what is a RSS?
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recombination signal seq
the heptamer, 12/23, nonamer complex 12/23 rule physical sig for dble helix DNA |
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what are the significance of the heptamer and nonamer?
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conserved, noncoding DNA
heptamer is palindromic; nonamer is A,T rich. recog by RAG 1,2 |
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what are RAG 1,2?
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enzymes; recombinase activating gene; fxns as pillow for the RSS activity and VDJ recombination;
1. recog RSS 2. forms RSS synapse-loop formmation 3. makes ss DNA nick-signal joint released |
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describe V(D)J recombination
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after signal joint released, free ends undergo transesterification->hairpin loop
cleavage of hairpin loop->ss DNA overhang P nucleotide addn w/ template jxnal fexibility-exonuclease N nucleotide addn w/ TdT in heavy chains only; non-templated coding ends align DNA polymerase fills gaps DNA ligase |
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what are the effects of V(D)J recombination? specifically, P-nuc, jxnal flex, and N-nuc addn?
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enhances diversity
can also cause frameshift, nonsense and missense mutations |
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where does V(D)J recombination occur?
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in the variable region, specifically the DJ/J regions which encode for AA making up CDR3
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what is allelic exclusion?
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ensures that each B cell will only produce 1 Ig
after a successful rearrangement is made, all other rearrangements for that region are inhibited after ~2 unsuccessful rearrangements the cell will die |
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what is the order of rearrangement for a pre-exposure Ig?
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heavy chain rearranged first
then kappa light if no kappa light rearrangements are successful, then lamba light |
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a mature, but naive, B cell is released with what Ig on its surface?
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if the Ig does not react to self while in the BM, it is released with BOTH IgM and IgD
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alternative mRNA splicing is responsible for what differentiations in Igs?
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alt mRNA spilicing leads to:
IgM v. IgD : they are ID except for their tail C region transmbr v secreted Ig both rely on polyadenylation seq |
