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: -Silent mutations occur when the change of a single DNA nucleotide within a protein-coding portion of a gene does not affect the sequence of amino acids that make up the gene’s protein.

Detailed explanation-4: -The mutations that do not have any effect on the phenotype are known as silent mutations. Thus, when no change occurs in the amino acid sequence in the protein it is known as point mutation or silent mutation.

Detailed explanation-5: -Such a substitution could: change a codon to one that encodes a different amino acid and cause a small change in the protein produced. For example, sickle cell anemia is caused by a substitution in the beta-hemoglobin gene, which alters a single amino acid in the protein produced.