GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Recombination
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Example Questions
Example Question #11 : Mutation And Variation
Which of the following methods results in no loss of information when repairing a double-stranded DNA break?
Translesion synthesis
Recombination
Non-homologous end joining
There is no way to prevent loss of information from a double-stranded break in DNA
Recombination
Recombination between homologous chromosomes is one of the only methods for repairing double-stranded breaks in DNA without losing information. This method only works, however, if there is an extra copy of the same DNA in the cell (i.e. on a homologous chromosome). Recombination is not possible prior to the S phase of the cell cycle, during which DNA is replicated.
Non-homologous end joining results in the deletion of a few base pairs, which can be problematic if done in the coding region of a gene. Translesion synthesis actually has nothing to do with double-stranded breaks, and refers to a method of accurately synthesizing DNA over mutations (such as thymine dimers) by using specialized polymerases.
Example Question #12 : Mutation And Variation
Genetic recombination occurs during __________ of meiosis I, and genetic information is exchanged between __________.
prophase I . . . non-sister chromatids
metaphase . . . non-sister chromatids
prophase I . . . sister chromatids
metaphase . . . crossover gametes
anaphase . . . sister chromatids
prophase I . . . non-sister chromatids
Recombination occurs between homologous chromosomes, not the sister chromatids, and this happens in prophase I of meiosis.
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