What is the Effect of a Nonsense Mutation in a Gene

Question

What is the effect of a nonsense mutation in a gene?
A) It changes an amino acid in the encoded protein.
B) It has no effect on the amino acid sequence of the encoded protein.
C) It introduces a premature stop codon into the mRNA.
D) It alters the reading frame of the mRNA.
E) It prevents introns from being excised.

Accepted Answer

A nonsense mutation introduces a premature stop codon into the mRNA, causing translation to stop prematurely and resulting in a truncated, nonfunctional protein.

Answer: B 
 A silent mutation would have no effect on the amino acid sequence of the encoded protein, whereas a nonsense mutation would introduce a premature stop codon, resulting in a truncated protein.

Answer: D 
 An insertion or deletion mutation could alter the reading frame of the mRNA, causing a frameshift mutation. A nonsense mutation would introduce a premature stop codon, but it would not necessarily alter the reading frame.

Answer: A, C 
 A missense mutation changes an amino acid in the encoded protein, whereas a nonsense mutation introduces a premature stop codon into the mRNA.