Lecture 05

Question 1

Meiotic recombination

Answer 1

1. Double strand break - identified by Spo11 or Mre11 and processing ends of break
2. Strand invasion and double Holliday junction formation
3. Resolution

Question 2

Holliday junction

Answer 2

DNA intermediate containing four DNA strands from two different helices

Question 3

Outcomes of Resolution in meiotic recombination

Answer 3

1. Crossing over

2. Gene conversion - most common

Question 4

Branch migration

Answer 4

After strand invasion, point of exchange causes movement. Can be spontaneous or catalyzed.

Question 5

Gene conversion

Answer 5

Divergence from expected allele distribution during meiosis - caused by DNA synthesis during homologous recombination, repair of mismatches in heteroduplex DNA

Question 6

DNA-only Transposons

Answer 6

Exist only as DNA, predominate in bacteria (responsible for antibiotic resistance), use cut-and-paste transposition or replicative transposition

Question 7

Retrovirus-like Transposons

Answer 7

Resemble retroviruses without a coat; move in/out of chromosomes but unable to leave resident cell. Reverse transcriptase makes dsDNA copy of RNA molecule and integrates into site of chromosome via integrase

Question 8

Nonretroviral Transposons

Answer 8

Use enzymes from other transposons; endonuclease nicks target DNA, ssDNA copy of L1 linked to target, dsDNA inserted at target site.

Question 9

Conservative site specific recombination

Answer 9

Mediates rearrangement of other types of mobile DNA elements; break/join DNA double helices