GENETICS AND EVOLUTION
MOLECULAR BASIS OF INHERITANCE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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can be repaired by the mismatch repair system
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will almost certainly lead to the death of the cell
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is virtually impossible, as the accuracy of DNA polymerase is such that errors almost never occur
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cannot be repaired, and a new mutation will invariably result
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Detailed explanation-1: -A third excision repair system recognizes mismatched bases that are incorporated during DNA replication. Many such mismatched bases are removed by the proofreading activity of DNA polymerase. The ones that are missed are subject to later correction by the mismatch repair system, which scans newly replicated DNA.
Detailed explanation-2: -Most of the mistakes during DNA replication are promptly corrected by DNA polymerase by proofreading the base that has been just added (Figure 14.6. 1). In proofreading, the DNA pol reads the newly added base before adding the next one, so a correction can be made.
Detailed explanation-3: -Mismatch repair is a process that corrects mismatched nucleotides in the otherwise complementary paired DNA strands, arising from DNA replication errors and recombination, as well as from some types of base modifications.
Detailed explanation-4: -Fortunately, cells have evolved highly sophisticated means of fixing most, but not all, of those mistakes. Some of the mistakes are corrected immediately during replication through a process known as proofreading, and some are corrected after replication in a process called mismatch repair.
Detailed explanation-5: -DNA replication is a highly accurate process, but mistakes can occasionally occur, such as a DNA polymerase inserting a wrong base. Uncorrected mistakes may sometimes lead to serious consequences, such as cancer. Repair mechanisms correct the mistakes.