Texas A&M University (TAMU) BICH 410 Comprehensive Biochemistry I Exam 1 Practice Test

A premature stop codon arises when a nonsense mutation introduces a stop signal directly into the coding sequence, so translation ends earlier than intended. This truncates the protein, often destroying its function because important regions are missing. In contrast, a missense mutation changes one codon to code for a different amino acid, altering the sequence but not necessarily shortening the protein. A silent mutation changes a codon to another that still codes for the same amino acid, leaving the protein sequence unchanged. Frameshift mutations, due to insertions or deletions that aren’t in multiples of three, shift the entire reading frame and can create a stop codon downstream, but the hallmark is the altered reading frame rather than the explicit insertion of a stop signal.