Help with Recombination - GRE Subject Test: Biochemistry, Cell, and Molecular Biology

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Question

Which of the following methods results in no loss of information when repairing a double-stranded DNA break?

Answer

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.

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Question

Genetic recombination occurs during __________ of meiosis I, and genetic information is exchanged between __________.

Answer

Recombination occurs between homologous chromosomes, not the sister chromatids, and this happens in prophase I of meiosis.

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