Podcast
Questions and Answers
Which protein forms a filament with ssDNA in eukaryotes and forces the ssDNA into an unusual configuration?
Which protein forms a filament with ssDNA in eukaryotes and forces the ssDNA into an unusual configuration?
What is the role of ATP hydrolysis in the process of HR?
What is the role of ATP hydrolysis in the process of HR?
What is the potential harm of HR?
What is the potential harm of HR?
Which protein mutations lead to a significantly increased frequency of breast and ovarian cancer?
Which protein mutations lead to a significantly increased frequency of breast and ovarian cancer?
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What is the role of HR in meiosis?
What is the role of HR in meiosis?
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What is crossover in meiosis?
What is crossover in meiosis?
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What is the role of crossover in meiosis?
What is the role of crossover in meiosis?
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During homologous recombination, DNA strands are exchanged between a pair of homologous duplex DNA. This process occurs when two daughter DNA molecules lie close together, and one of them serves as a template. What is the hallmark of this process?
During homologous recombination, DNA strands are exchanged between a pair of homologous duplex DNA. This process occurs when two daughter DNA molecules lie close together, and one of them serves as a template. What is the hallmark of this process?
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How does homologous recombination accurately repair double-strand breaks (DSBs)?
How does homologous recombination accurately repair double-strand breaks (DSBs)?
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What happens during strand exchange/invasion in homologous recombination?
What happens during strand exchange/invasion in homologous recombination?
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Which protein is responsible for carrying out strand exchange/invasion in homologous recombination?
Which protein is responsible for carrying out strand exchange/invasion in homologous recombination?
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When does homologous recombination occur during the cell cycle?
When does homologous recombination occur during the cell cycle?
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What does HR stand for in the context of DNA repair?
What does HR stand for in the context of DNA repair?
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What role does polymerase play in homologous recombination?
What role does polymerase play in homologous recombination?
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Which type of DNA damage is especially dangerous and can cause the breakdown of chromosomes into smaller fragments?
Which type of DNA damage is especially dangerous and can cause the breakdown of chromosomes into smaller fragments?
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What are the two mechanisms to repair double-strand breaks?
What are the two mechanisms to repair double-strand breaks?
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Which repair mechanism predominates in humans?
Which repair mechanism predominates in humans?
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When does homologous recombination (HR) occur in the cell?
When does homologous recombination (HR) occur in the cell?
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What is the three-step repair process of non-homologous end joining (NHEJ)?
What is the three-step repair process of non-homologous end joining (NHEJ)?
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Which repair mechanism usually causes deletions and is common in mammalian somatic cells?
Which repair mechanism usually causes deletions and is common in mammalian somatic cells?
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Which repair mechanism is used when sister chromatids are available to serve as templates?
Which repair mechanism is used when sister chromatids are available to serve as templates?
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True or false: NHEJ is common and has very low accuracy.
True or false: NHEJ is common and has very low accuracy.
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True or false: DSB is mainly repaired by HR since HR is more accurate than NHEJ.
True or false: DSB is mainly repaired by HR since HR is more accurate than NHEJ.
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True or false: The hallmark for HR is base pairing.
True or false: The hallmark for HR is base pairing.
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True or false: HR happens throughout the cell’s life cycle.
True or false: HR happens throughout the cell’s life cycle.
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True or false: HR only happens between sister chromatids, not between chromosomes, since they are too far away.
True or false: HR only happens between sister chromatids, not between chromosomes, since they are too far away.
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True or false: Although the formation of Holliday Junctions is rare, it is essential for chromosome crossover.
True or false: Although the formation of Holliday Junctions is rare, it is essential for chromosome crossover.
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True or false: Loss of heterozygosity (LOH) happens when HR occurs between sister chromatids.
True or false: Loss of heterozygosity (LOH) happens when HR occurs between sister chromatids.
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True or false: Gene conversion is an outcome of the coordination of HR and mismatch repair.
True or false: Gene conversion is an outcome of the coordination of HR and mismatch repair.
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True or false: Gene conversion could happen thousands of nucleotide pairs away from the DSB site due to 'branch migration'.
True or false: Gene conversion could happen thousands of nucleotide pairs away from the DSB site due to 'branch migration'.
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True or false: During cell meiosis, programmed DSB is the first step of the HR process. It happens between sister chromatids.
True or false: During cell meiosis, programmed DSB is the first step of the HR process. It happens between sister chromatids.
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Study Notes
Homologous Recombination (HR) and Repair Mechanisms
- HR forms a filament with ssDNA in eukaryotes, forcing ssDNA into an unusual configuration, with Rad51 protein playing a crucial role in this process.
Role of ATP Hydrolysis and Potential Harm of HR
- ATP hydrolysis is essential for the HR process, providing the energy required for DNA strand exchange and repair.
- The potential harm of HR lies in its potential to introduce errors or gene conversions, which can lead to genetic disorders or diseases like breast and ovarian cancer, especially when proteins like BRCA1 and BRCA2 are mutated.
Role of HR in Meiosis and Crossover
- HR plays a crucial role in meiosis, as it facilitates crossover events, which increase genetic diversity by shuffling alleles and creating new combinations.
- Crossover is the exchange of genetic material between homologous chromosomes, leading to new allelic combinations and increasing genetic diversity.
Mechanisms of Homologous Recombination and Non-Homologous End Joining (NHEJ)
- HR accurately repairs double-strand breaks (DSBs) by exchanging DNA strands between homologous duplex DNA molecules.
- The hallmark of HR is the formation of a Holliday Junction, where two DNA molecules are joined together.
- Strand exchange/invasion occurs when a broken DNA strand invades a homologous template, displacing one strand, and creating a displacement loop (D-loop).
- Rad51 and other recombinases are responsible for carrying out strand exchange/invasion in HR.
- HR occurs during the S and G2 phases of the cell cycle, when sister chromatids are available as templates.
- NHEJ, on the other hand, is a faster but less accurate repair mechanism that predominates in humans, involving a three-step process: end recognition, end processing, and ligation.
Double-Strand Break (DSB) Repair Mechanisms
- DSBs are especially dangerous and can cause chromosome fragmentation.
- There are two primary mechanisms to repair DSBs: HR and NHEJ.
- NHEJ usually causes deletions and is common in mammalian somatic cells, while HR is more accurate but slower and more complex.
- HR is used when sister chromatids are available to serve as templates, while NHEJ is used when no template is available.
True or False Statements
- True: NHEJ is common and has low accuracy.
- True: DSB is mainly repaired by HR since HR is more accurate than NHEJ.
- False: The hallmark for HR is base pairing.
- False: HR happens throughout the cell’s life cycle.
- False: HR only happens between sister chromatids, not between chromosomes, since they are too far away.
- True: Although the formation of Holliday Junctions is rare, it is essential for chromosome crossover.
- False: Loss of heterozygosity (LOH) happens when HR occurs between sister chromatids.
- True: Gene conversion is an outcome of the coordination of HR and mismatch repair.
- True: Gene conversion could happen thousands of nucleotide pairs away from the DSB site due to 'branch migration'.
- True: During cell meiosis, programmed DSB is the first step of the HR process, which happens between sister chromatids.
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Description
Understanding the Role of Rec A in DNA Strand Exchange and Invasion: Test your knowledge on the crucial steps and mechanisms involved in Rec A-mediated strand exchange and invasion in eukaryotes. Explore how Rec A forms a protein-DNA filament, destabilizes duplex DNA, and samples the sequence for base-pairing to facilitate successful DNA repair. Get ready to dive into the molecular biology of Rec A and its ATP hydrolysis activity!
