AP BIOLOGY

Detailed explanation-1: -A nonsense mutation occurs in DNA when a sequence change gives rise to a stop codon rather than a codon specifying an amino acid. The presence of the new stop codon results in the production of a shortened protein that is likely non-functional.

Detailed explanation-2: -Stop codons are also called nonsense codons because they do not code for an amino acid and instead signal the end of protein synthesis. Thus, nonsense mutations occur when a premature nonsense or stop codon is introduced in the DNA sequence.

Detailed explanation-3: -A point mutation could be a silent mutation, maintaining the original amino acid sequence and the resulting protein. A frameshift mutation is more likely to result in a nonfunctional protein.

Detailed explanation-4: -When the mRNA stop codon is reached, the fully synthesized protein does not simply fall off the ribosome. Release factors (RFs) are the protein assistants that recognize the presence of a stop codon in the ribosomal A-site and trigger cleavage of the polypeptide from the P-site tRNA (Fig.

Detailed explanation-5: -(NON-sens myoo-TAY-shun) A genetic alteration that causes the premature termination of a protein. The altered protein may be partially or completely inactivated, resulting in a change or loss of protein function.