AP BIOLOGY

Detailed explanation-1: -Incorrectly paired nucleotides that still remain following mismatch repair become permanent mutations after the next cell division. This is because once such mistakes are established, the cell no longer recognizes them as errors.

Detailed explanation-2: -The mutation rate of stable genomes is estimated to be 10−10/bp per cell generation (3). However, in certain physiologic conditions the rate of mutation increases dramatically. As one example, the immunoglobulin (Ig) genes can undergo mutation at a rate that exceeds the basal rate by more than a million-fold (1, 4, 5).

Detailed explanation-3: -These mutations are called mismatches because they are positions where the nucleotide that is inserted into the daughter polynucleotide does not match, by base-pairing, the nucleotide at the corresponding position in the template DNA (Figure 14.2A).

Detailed explanation-4: -Errors in DNA Replication The addition of an incorrect base can take place by a process called tautomerization. A tautomer of a base group is a slight rearrangement of its electrons that allows for different bonding patterns between bases. This can lead to the incorrect pairing of C with A instead of G, for example.