AP BIOLOGY

Detailed explanation-1: -A nucleotide change in the DNA that does not result in an amino acid change in the protein is called a “synonomous” or “silent” mutation (see Figure 3.3).

Detailed explanation-2: -Silent mutations are base substitutions that result in no change of the amino acid or amino acid functionality when the altered messenger RNA (mRNA) is translated. For example, if the codon AAA is altered to become AAG, the same amino acid – lysine – will be incorporated into the peptide chain.

Detailed explanation-3: -A nucleotide substitution that changes the corresponding amino acid in the protein is called a nonsynonymous substitution (denoted as KA), whereas a nucleotide substitution that does not change the amino acid in the protein is called a synonymous substitution (denoted as KS).

Detailed explanation-4: -Point mutations that alter the resulting protein sequences are called nonsynonymous mutations, while those that do not alter protein sequences are called silent or synonymous mutations. Between one-quarter and one-third of point mutations in protein-coding DNA sequences are synonymous.

Detailed explanation-5: -A silent mutation (quiet mutation) is a form of mutation that does not cause a major change in the amino acid. As a result, the protein remains active and functional. Because of this, the changes are viewed as though they are neutral in terms of evolution.