Chiolo Lecture 8 Flashcards
What are the critical components required to initiate HR repair?
- CtIP
- Brca2
- Rad51
What are the steps to HR repair?
- MRN and CTIP start resection
- Brca2 recruits Rad51
- Rad51 mediates strand invasion
How are HR and NHEJ regulated?
by CDKs (cyclin-dependent kinases) through the phosphorylation of HR targets
What causes NHEJ to occur in the G1 phase?
Brca2 is phosphorylated by CDK-G1 cyclins
What causes HJ to occur in the S/G2 phase?
CtIP is phosphorylated by CDK-S/G2 cyclins
What causes the chromatin to be more accessible for repair?
chromatin remodeling and acetylation
What causes chromatin sliding?
ATP hydrolysis
What is the function of chromatin remodelers?
- change site accessibility via sliding, ejection, and dimer exchange
- promote strand invasion by providing access to the donor sequence
When are histones lost?
- during resection
- during strand invasion
What leads to diploid cells in mitosis?
replication followed by cell division
What are the phases of mitosis?
- interphase
- prophase
- metaphase
- anaphase
- telophase
- cytokinesis
What leads to haploid cells in meiosis?
replication followed by 2 mitotic divisions
What are the steps to meiosis?
- meiotic interphase/ prophase 1
- metaphase 1
- anaphase II
- metaphase II
- anaphase II
What separation happens in meiosis I?
separation of homologous chromosomes
What separation happens in meiosis II?
separation of sister chromatids
What is required for proper chromosome alignment and segregation in meiosis?
homologous recombination with crossover
What happens during recombination in meiosis?
- numerous DSBs are induced and at least one results in cross over for each chromosome pair
- one crossover interferes with the occurrence of another crossover in the sample pair of chromosomes (C.O. interference)
What is the function of SpoII?
a tyrosine of SpoII covalently binds to 5’ phosphate of the DNA backbone to generate a meiotic DSB
Is ATP needed for Spo11 meiotic DSB generation?
no ATP is needed
What is the function of Dmc1?
promotes the use of homologous chromosomes in meiosis
What is the process of recombination in meiosis?
- SpoII generates DSBs
- MRN complex and CtIP resects
- Spo11 is removed by resection
- Dmc1 and Rad51 facilitates strand invasion
- recombination
What leads to non-Mendelian allele segregation?
gene conversion in the heteroduplex DNA
How does gene targeting occur?
by homologous recombination and is promoted by a DSB at the target locus
What do homologous sequences induce in yeast?
dHj-mediated integration
What do DSBs promote in human cells?
SSA-mediated integration
What is CRISPR/Cas9?
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
How is CRISPR/Cas9 used as a research tool?
Cas9 can be directed to any target sequence to induce DSBs and improve gene targeting
