30 - B CELLS 4 Flashcards
location of genes for heavy and light chains of Ig
the heavy and light chain gene families are encoded on separate chromosomes
what is somatic recombination and what does it result in
which regions are present in the light vs heavy chain
where are CDR 1, 2, and 3 encoded
what happens during B cell development
how is the light chain DNA organized and expressed
how is the heavy chain DNA organized and expressed
what is the process that happens from DNA to BCR of naive B cell
how many regions are there to choose from for the V, D and J regions
46V regions
23D regions
6J regions
what is recombination signal sequences (RSSs) and what do they do
how does the recombination work through RSSs
- RSS regions are brought together, creating a loop in the DNA
the loop part contains the segments that were not selected - RAG: recombination activating gene
RAG1 and RAG2 are necessary for recombination: recognise and cut DNA at the Ig-encoding region and the RSS
covalently closed DNA hairpin ends - loop is excised (signal joint)
no longer on the chromosome, will get deleted
coding region of selected V and J regions remain (coding joint)
what is junctional diversity
what happens in junctional diversity
steps of hairpin cleavage in junctional diversity
Artemis can open the hairpin in 3 different ways
- addition of palindromic nucleotides at overhangs
this creates a template and DNA repair enzymes fill in the complementary strand
happens mainly in the light chain
- exonuclease activity may remove nucleotides on each side of the coding joint
- terminal deoxynucleotidyl transferase (TdT) adds up to 20 N-nucleotides (non template encoded) to the cleaved strands primary in heavy chain: this is the reason as to why CDRs vary in length
repair enzymes then trim off non-matching nucleotides, fill in remaining single stranded gaps and ligate the new DNA
summary of junctional diversity
summary of the mechanisms that generate BCR diversity in naive B cells
summary
