If a codon that codes for glycine becomes a codon for alanine, this is

If a codon that codes for glycine becomes a codon for alanine, this is

• A. Missense mutation
• B. Nonsense mutation
• C. Silent mutation
• D. Frameshift mutation

Answer: (A)

Changing a codon to code for a different amino acid produces a missense mutation. Here, one nucleotide change makes the glycine codon specify alanine instead, so the protein would incorporate a different amino acid at that position. It’s not a silent mutation because the amino acid actually changes, not stays the same; it’s not a nonsense mutation because no stop codon is created; and it’s not a frameshift because the reading frame of all downstream codons isn’t altered. In this case, a single-nucleotide substitution (glycine codon to alanine codon) alters the protein sequence, which is the essence of a missense mutation.

Changing a codon to code for a different amino acid produces a missense mutation. Here, one nucleotide change makes the glycine codon specify alanine instead, so the protein would incorporate a different amino acid at that position. It’s not a silent mutation because the amino acid actually changes, not stays the same; it’s not a nonsense mutation because no stop codon is created; and it’s not a frameshift because the reading frame of all downstream codons isn’t altered. In this case, a single-nucleotide substitution (glycine codon to alanine codon) alters the protein sequence, which is the essence of a missense mutation.