How might a single base substitution in the sequence of a gene affect the amino acid sequence of a protein encoded by the gene, and why?
A) The amino acid sequence would be substantially altered, because the reading frame would change with a single base substitution.
B) It is not possible for a single base substitution to affect protein structure, because each codon is three bases long.
C) Only a single amino acid could change, because the reading frame is unaffected.
D) All amino acids following the substitution would be affected, because the reading frame would be shifted.

Question

Quizplus · Accepted Answer

A single base substitution, or point mutation, only affects the codon in which it occurs, and therefore only the corresponding amino acid in the protein sequence. The reading frame is not affected by a single base substitution. Only in the case of a frameshift mutation, where one or more nucleotides are added or deleted, would the reading frame be shifted and result in a significant change in the amino acid sequence.

How Might a Single Base Substitution in the Sequence of a Gene