Chiolo Lecture 6

Question 1

What is branch migration?

Answer 1

extends the length of the DNA exchanged

Question 2

What are the different pathways of homologous recombination?

Answer 2

1. Single-Strand Annealing
2. Double-Holliday Junction
3. Synthesis-Dependent Strand Annealing
4. Break-Induced Replication

Question 3

What does Single-Strand Annealing (SSA) use?

Answer 3

30-100 bp of homology to rejoin the two ends of the DSB and results in large deletions

Question 4

What are the characteristics of SSA?

Answer 4

1. 30-100 bp homology
2. works at long distance
3. can lead to large deletion

Question 5

What are the characteristics of Alt-EJ?

Answer 5

1. > 4 bp homology
2. works at short distance
3. results in small deletions

Question 6

Does SDSA require Double-Holliday Junctions?

Answer 6

does not require Double-Holliday Junctions

Question 7

What does mating-type switching of S.cerevisiae occur by?

Answer 7

SDSA repair

Question 8

What is present at MAT locus

Answer 8

“Ya” or “Yα” gene is present, and expressed, determining the mating type

Question 9

What shares sequence homology?

Answer 9

MAT, HML, HMR

Question 10

What brings HMR and MAT in proximity?

Answer 10

a DNA loop

Question 11

What repairs collapsed forks?

Answer 11

break-induced replication (BIR)

Question 12

What is the process of BIR?

Answer 12

1. rescues a collapsed replication fork by strand invasion
2. information is copied out of newly synthesized DNA
3. BIR results in extensive loss of heterozygosity

Question 13

What can lead to loss over heterozygosity during the cell cycle?

Answer 13

crossover during mitotic recombination

Question 14

What results from loss of heterozygosity of the Rb gene?

Answer 14

retinoblastoma

Question 15

What is retinoblastoma?

Answer 15

most common malignant tumor of the eye in children

Question 16

What is the process of mate-type switching?

Answer 16

1. the pathway is activated by introducing double-strand breakage in DNA at the MAT locus by HO endonuclease
2. Using the DNA at either the silent HML or HMR site as a template, homology-directed repair copies a sequence

Question 17

What is the process of synthesis-dependent strand annealing? (SDSA)?

Answer 17

1. resection
2. strand invasion
3. D-loop
4. Single Holliday Junction
5. synthesis proceeds from the template strand, and the D-loop translocates along the template strand
6. the newly synthesized strand pairs with the complementary strand of the damaged duplex on the other side of the break
7. the damaged duplex now contains a region of single-stranded DNA rather than a double strand gap
8. the gap is filled using the newly synthesized strand as a template