Questions and Answers
What is the major modification proposed by the Double-strand Break Model to the Holliday model?
What is the primary function of the protein Spo11 in Saccharomyces cerevisiae?
What is the outcome of the double-strand break model?
What is the number of proteins required for the formation of DNA double-strand breaks in Saccharomyces cerevisiae?
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What is the stage of recombination where the double-strand break model is involved?
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What is the name of the model that proposes two nicks in the same location on two strands?
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What is the result of the DNA gap repair synthesis?
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What is the molecular mechanism that occurs after the formation of DNA double-strand breaks?
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What is the term used to describe the phenomenon in which one allele is converted to the allele on the homologous chromosome?
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What is the structure formed during homologous recombination that has been called a chi (χ) form?
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What is the process by which the Holliday junction is resolved?
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What occurs during branch migration in homologous recombination?
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What is the region of DNA that contains a mix of genetic information from both parental chromosomes?
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What is the model of homologous recombination that involves the formation of a double-strand break?
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What is the term used to describe the exchange of corresponding segments between homologous chromosomes?
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What is the process by which homologous chromosomes align and exchange genetic information?
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What is the initial event in the homologous recombination process according to the Holliday model?
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What is the result of the branch migration process?
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What is the role of the Holliday junction in the homologous recombination process?
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What is the final event in the homologous recombination process?
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What is the term used to describe the process of a DNA strand in one helix being swapped for a DNA strand in the other helix?
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What is the result of the covalent linkage between the invading strands and the complementary strands?
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What is the term used to describe a region of double-stranded DNA that contains one or more base-pair mismatches?
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What is the double-strand break model an example of?
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Study Notes
Refined Models of Recombination
- More recent models have modified the initiation phase of recombination, proposing that a DNA helix incurs a break in both strands of one chromatid, rather than two nicks in the same location on two strands.
- The double-strand break model was proposed by Jack Szostak, Terry Orr-Weaver, Rodney Rothstein, and Franklin Stahl, requiring DNA gap repair synthesis.
Proteins Facilitating Homologous Recombination
- Double-strand breaks initiate homologous recombination in meiosis, creating sites where a crossover will occur.
- In Saccharomyces cerevisiae, at least 10 different proteins are required for double-strand breaks, including Spo11, which breaks the DNA.
- Homologous recombination is found in all species, and each species may have multiple molecular mechanisms for it.
The Holliday Model
- The Holliday model involves the alignment of two homologous chromatids, with a break or nick occurring at identical sites in one strand of each chromatid.
- The strands then invade the opposite helices and base-pair with the complementary strands, creating a Holliday junction.
- The Holliday junction can migrate laterally, causing a swap of DNA strands between the two helices, potentially producing a heteroduplex with base-pair mismatches.
- The final step is resolution, where two DNA strands break and rejoin to create two separate chromosomes.
Homologous Recombination
- Homologous recombination involves crossing over between identical or homologous regions of chromosomes, occurring in meiosis I and occasionally during mitosis.
- It involves the alignment of a pair of homologous chromosomes, followed by breakage at analogous locations and exchange of corresponding segments.
- Crossing over between sister chromatids is called sister chromatid exchange (SCE), which does not produce new combinations of alleles.
- Crossing over between homologous chromosomes can result in genetic recombination, producing new combinations of alleles.
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Description
This quiz covers the refinement of the Holliday model of genetic recombination, including the initiation phase and the double-strand break model. It discusses the likelihood of DNA helix breaks and the proposals of Jack Szostak, Terry Orr-Weaver, and Rodney Rothstein.
