Lecture 4

Question 1

What is the order of somatic recombination in a HBD chain?

Answer 1

D-J, then V-DJ

Question 2

What are the three methods of generating V region diversity?

Answer 2

Method 1: random selection of gene segments in V region, and any VDJ segment can join together
Method 2: any H with any L chain, or any a+b, g+d
Method 3: insertion of P and N nucleotides

Question 3

What are the three proteins involved in joining VDJ segments together?

Answer 3

RAG-1 and RAG-2, DNA repair enzyme, TdT

Question 4

What is RAG-1/RAG-2?

Answer 4

recombination activation genes
- cuts DNA and leaves hairpins
- only present in developing lymphocytes

Question 5

What is DNA repair enzyme?

Answer 5

takes two pieces of DNA and ligates to form one piece

Question 6

What is TdT?

Answer 6

processes the ends of DNA by adding nucleotides once the hairpin has been opened (N nucleotides)

Question 7

How does RAG-1/2 recognize the beginning and ends of the V(D)J segments that are to be recombined?

Answer 7

recognizes RSS, which have nine and seven bps plus either a 12 or 23 nucleotide spacer

Question 8

What is the role of the DNA repair enzymes after RAG-1/2 splicing happens?

Answer 8

forms the signal joint by rejoining the ends of the DNA to be discarded, then opens the hairpins by randomly cutting near hairpin

Question 9

What is the role of DNA POL after the DNA repair enzyme makes the cut and TdT adds N nucleotides?

Answer 9

adding complimentary base pairs

Question 10

Why don’t B cells’ light chains get N nucleotides?

Answer 10

B cell stops expressing TdT after it rearranges the H chain and before the light chain

Question 11

How do B Cells and T Cells differ in TdT expression?

Answer 11

T cells express TdT throughout development

Question 12

What gets rid of the extra nucleotides when the DNA is getting repaired?

Answer 12

DNA POL