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

Question

Quizplus · Accepted Answer

A single base substitution in a gene may cause a substitution of a different nucleotide (e.g. A to G or C to T), which can change the codon for an amino acid. However, since the genetic code is a degenerate code, where multiple codons can code for the same amino acid, a single base substitution may not always cause a change in the amino acid sequence of the protein encoded by the gene. Additionally, since the genetic code is read in groups of three, or codons, a single base substitution would only affect the codon in which it occurs and would not affect the reading frame of the gene. Therefore, only one amino acid could change as a result of the single base substitution, and the reading frame of the gene would not be affected.

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