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 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-3: -Silent mutations do not affect the sequence of amino acids during translation. Nonsense mutations result in a stop codon where an amino acid should be, causing translation to stop prematurely. Missense mutations change the amino acid specified by a codon.

Detailed explanation-4: -Mutations that cause the altered codon to produce an amino acid with similar functionality (e.g. a mutation producing leucine instead of isoleucine) are often classified as silent; if the properties of the amino acid are conserved, this mutation does not usually significantly affect protein function.

Detailed explanation-5: -Non-silent mutations include missense mutations which change an amino acid to another amino acid, nonsense mutations which change an amino acid to a stop codon, mutations in splice sites and insertions or deletions (indels).