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15 Cards in this Set

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GOD in pre-Ag exposure occurs where?
post-Ag exposure?
pre-Ag: Bone marrow
Post-Ag: peripheral lymphoid tissues
each Ig is encoded on how many chromosomes?
3 separate gene complexes on 3 diff chromosomes: 1 complex each for lamdba light, kappa light, and heavy chains.
how many gene segments are req for the variable region?
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)
what is a leader sequence?
it comes before the V segment for each gene encoding for the variable region; it directs the protein after synthesis
describe the formation of a lambda light chain? kappa light? heavy?
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
what is a RSS?
recombination signal seq
the heptamer, 12/23, nonamer complex
12/23 rule
physical sig for dble helix DNA
what are the significance of the heptamer and nonamer?
conserved, noncoding DNA
heptamer is palindromic; nonamer is A,T rich. recog by RAG 1,2
what are RAG 1,2?
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
describe V(D)J recombination
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
what are the effects of V(D)J recombination? specifically, P-nuc, jxnal flex, and N-nuc addn?
enhances diversity
can also cause frameshift, nonsense and missense mutations
where does V(D)J recombination occur?
in the variable region, specifically the DJ/J regions which encode for AA making up CDR3
what is allelic exclusion?
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
what is the order of rearrangement for a pre-exposure Ig?
heavy chain rearranged first
then kappa light
if no kappa light rearrangements are successful, then lamba light
a mature, but naive, B cell is released with what Ig on its surface?
if the Ig does not react to self while in the BM, it is released with BOTH IgM and IgD
alternative mRNA splicing is responsible for what differentiations in Igs?
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