B cell activation

Question 1

How does somatic recombination begin?

Answer 1

randomly choose one of each. Sections contain recombination signal sequences that are either 23 or 12 bp long. If the RSSes are different, they can align parallelly

Question 2

How are RSSes removed?

Answer 2

Aligned RSSes are removed by RAG-1/RAG-2 in the V(D)J recombinase enzyme complex
One arm recognises 23 bp and the other recognises 12. This forms a signal joint (part that is excised) and a coding joint (part that remains)

Question 3

How are coding regions formed

Answer 3

There is a hairpin formed after the signal joint is cleaved out. This is opened up by the Artemis complex dsDNA -> ssDNA. N nucleotides are added by TdT until the two strands can pair, non-paired are cut out with exonucleases, and gaps are filled by ligation

Question 4

What region has the highest diversity and why?

Answer 4

HV3/CDR3, because its at this site that the J region binds to the V region

Question 5

What does Artemis DNA-PK complex generate

Answer 5

palindromic P-nucleotides