AP BIOLOGY

Detailed explanation-1: -In genetics, a nonsense mutation is a point mutation in a sequence of DNA that results in a premature stop codon, or a nonsense codon in the transcribed mRNA, and in leading to a truncated, incomplete, and nonfunctional protein product.

Detailed explanation-2: -These 20 amino acids are organized in a linear way and this linear structure of proteins is known as the primary structure. Any change (genetic mutation) in the primary structure of a protein can cause a sequence change in the linear amino acid chain. Hence, option (d) is accurate.

Detailed explanation-3: -The impact of nonsense mutations is two-fold: (1) the PTC-containing mRNA is degraded by a surveillance pathway called nonsense-mediated mRNA decay (NMD) and (2) protein translation stops prematurely at the PTC codon, and thus no functional full-length protein is produced.

Detailed explanation-4: -A nonsense mutation, or its synonym, a stop mutation, is a change in DNA that causes a protein to terminate or end its translation earlier than expected. This is a common form of mutation in humans and in other animals that causes a shortened or nonfunctional protein to be expressed.