Chapter 25 Quiz Questions

Question 1

1. Compare and contrast site specific recombination and transposition.

Answer 1

1. SSR: Does not introduce new pieces of DNA; uses cre binding sites and region of strand exchange, uses recombinase proteins. 2. Tranposition: Jumping genes, excisable segments of DNA, uses Inverted repeats and insertion sequences, key enzyme transpoase,

Question 2

2. Understand how inversions, deletions and insertions can be produced by
   site specific recombination (CSSR).

Answer 2

Inversions occur when the directionality of the ROSE are pointed in the opposite direction for two pieces of DNA. Correct excision occurs on two pieces of DNA if they point in the same direction. Inversions can also occur on a single piece of DNA if the recombination sites are pointing in the opposite direction (towards each other). Deletions and insertions occur on single stranded DNA if the recombination sequences are pointing in the same direction.

Question 3

3 VJ recombination process

Answer 3

1) RSS sequence associated with V segment and J segment 2) Recombinase binds to RSS sequence on V and J. 3) Rag1/2 form 3’OH and the 3’OH does a nucleophilic attack on its own strand watson-crick strand. 4) The genetic information in the middle gets removed.

Question 4

3 VDJ Recombination

Answer 4

1) RAG 1/2 binds to V and D RSS 2) cleavage produces 3’OH 3) 3’OH attacks own watson crick strand 4) Ku70/80 involved in joining. Artemis opens hairpins and activates Ku70/80,

Question 5

SQ # 1 What is CSSR, and why is it considered conservative?

Answer 5

CSSR also known as site specific recombination is a method of genetic exchange between homologous pieces of DNA, and they do not include the introduction of new genetic material.

Question 6

SQ # 2 How do tyrosine recombinases differ from serine recombinases

Answer 6

tyrosine recombinases produce 5’OH overhangs, while serine recombinases produce 3’OH