Chiolo Lecture 8

Question 1

What are the critical components required to initiate HR repair?

Answer 1

1. CtIP
2. Brca2
3. Rad51

Question 2

What are the steps to HR repair?

Answer 2

1. MRN and CTIP start resection
2. Brca2 recruits Rad51
3. Rad51 mediates strand invasion

Question 3

How are HR and NHEJ regulated?

Answer 3

by CDKs (cyclin-dependent kinases) through the phosphorylation of HR targets

Question 4

What causes NHEJ to occur in the G1 phase?

Answer 4

Brca2 is phosphorylated by CDK-G1 cyclins

Question 5

What causes HJ to occur in the S/G2 phase?

Answer 5

CtIP is phosphorylated by CDK-S/G2 cyclins

Question 6

What causes the chromatin to be more accessible for repair?

Answer 6

chromatin remodeling and acetylation

Question 7

What causes chromatin sliding?

Answer 7

ATP hydrolysis

Question 8

What is the function of chromatin remodelers?

Answer 8

1. change site accessibility via sliding, ejection, and dimer exchange
2. promote strand invasion by providing access to the donor sequence

Question 9

When are histones lost?

Answer 9

1. during resection
2. during strand invasion

Question 10

What leads to diploid cells in mitosis?

Answer 10

replication followed by cell division

Question 11

What are the phases of mitosis?

Answer 11

1. interphase
2. prophase
3. metaphase
4. anaphase
5. telophase
6. cytokinesis

Question 12

What leads to haploid cells in meiosis?

Answer 12

replication followed by 2 mitotic divisions

Question 13

What are the steps to meiosis?

Answer 13

1. meiotic interphase/ prophase 1
2. metaphase 1
3. anaphase II
4. metaphase II
5. anaphase II

Question 14

What separation happens in meiosis I?

Answer 14

separation of homologous chromosomes

Question 15

What separation happens in meiosis II?

Answer 15

separation of sister chromatids

Question 16

What is required for proper chromosome alignment and segregation in meiosis?

Answer 16

homologous recombination with crossover

Question 17

What happens during recombination in meiosis?

Answer 17

1. numerous DSBs are induced and at least one results in cross over for each chromosome pair
2. one crossover interferes with the occurrence of another crossover in the sample pair of chromosomes (C.O. interference)

Question 18

What is the function of SpoII?

Answer 18

a tyrosine of SpoII covalently binds to 5’ phosphate of the DNA backbone to generate a meiotic DSB

Question 19

Is ATP needed for Spo11 meiotic DSB generation?

Answer 19

no ATP is needed

Question 20

What is the function of Dmc1?

Answer 20

promotes the use of homologous chromosomes in meiosis

Question 21

What is the process of recombination in meiosis?

Answer 21

1. SpoII generates DSBs
2. MRN complex and CtIP resects
3. Spo11 is removed by resection
4. Dmc1 and Rad51 facilitates strand invasion
5. recombination

Question 22

What leads to non-Mendelian allele segregation?

Answer 22

gene conversion in the heteroduplex DNA

Question 23

How does gene targeting occur?

Answer 23

by homologous recombination and is promoted by a DSB at the target locus

Question 24

What do homologous sequences induce in yeast?

Answer 24

dHj-mediated integration

Question 25

What do DSBs promote in human cells?

Answer 25

SSA-mediated integration

Question 26

What is CRISPR/Cas9?

Answer 26

a prokaryotic immune system: exposure to a viral DNA results in a guide-RNA (gRNA) that directs the Cas9 endonuclease to the DNA of the virus

Question 27

How is CRISPR/Cas9 used as a research tool?

Answer 27

Cas9 can be directed to any target sequence to induce DSBs and improve gene targeting