chapter 6 b - recombination Flashcards
(22 cards)
Abs come in isotypes (aka flavprs) that have different strictures and specialities what are these isotypes?
they have 5 different CH segments and 5 different heavy chain segment
IgM - mew
IgD - delta
IgG - gamma
IgE - epsilon
IgA - alpha
how is the selction of B cell done? how does clonal selction occur?
based on how the Ag interacts with the BCR proliferation and differentiation occur
in the light chain what can be said about the V and C regions
the V regions in DNA are different
the C regions are cosntant (same)
what are myelomas? what do they secret?
plasma cancer cells
they secret the same IgL (light chain)
what is just the IgL called?
Bence Jones proteins
2 types of light chain x 2 parents = 4 possible C gene alleles
light and heavy chains are encoded for by multiple gene segments that form 1 gene; these gene segments are shuffled to form the Ag binding region or the ____
V domain
how does rearrangement in the light chain work?
we lose gentic material between the V and J zones
how does reaaragnmnet in the heavy chain work?
lose gentic material between D and J segments and then between the DJ and V segemnts
where does early B cell development occur? independent of what?
in the BM is where the light and heavy chains reaarnage and it is indepednent of the antigen
what is joining regulated by?
the RSS segments on the DNA
what is the rule the RSS segemsnt follow?
the 12/23 rule meaning a 12 RSS can only join with a 23 RSS
whats the difference between productive and non-productive reaarangment?
productive - makes a protein
non-productive - no proatein can be created
what enzymes are responisble for joining and cutiing of DNA
RAG1 and RAG2
Recombination-activating Gene
other prteins repair the cut ends
how many gene segemnst exist in the light chain vs the heavy chain?
2 and 3
when is the heavy cahin expressed and when is the light chain expressed?
heavy - pre-B cell
light naive B-cell
how does RAG1/2 work?
it recognized the RSS regions to join and cut
how does the process of DNA rearrangement work
- cleave at the 5prime end
- sequences at the signal junction results from the joining of the two heptameric regions
- usualy a 3 prime over hang
4.cleavage of the hairpin generates sites for P nucleotide addition - in heavy chains we losee some P nucleotides and N nucleotides are added
P and N nucleotides increase diveristy
what happens if the V and J recombinant regions lie in the same direction? ( so they face each other)
when splicing the DNA and recombining it we form a loop of DAN instead of a line, this loop is then lost after fruther cell divisons
we still have one starnd produced with correct orientnetaion
the signal join is lost
what happens if the V and J recombinant regions lie in the opposite direction? ( so they face away from each other)
when we splice the DNA we are able to invert a part so it fits and that the signal joint can reamin in the genomic DNA
how does the cell deal with extra DAN that does not contribute to the Ig?
the signal joint remain in the DNA upstream of the recombinent antibidy gene
it ignores it through RNA processing
DNA
Precursor-mRNA
Processed-mRNA
how can a B cekk express membrane and secrtion forms of the same Ab?
due to RNA processing
what are the mechanism of diversity during B cell development?
-combinatorial diveristy
V x D x J or V x J
- junctional diveristy
flexible joining at RSS sequence
P and N nucleotide addition - combinatorial pairing of the heavy and the light chains
