Problem 2 - AP Psychology Premium Prep 2021

Question

A eukaryotic gene, which does not normally undergo splicing, was exposed to benzopyrene, a known carcinogen and mutagen. Following exposure, the protein encoded by the gene was shorter than before exposure. Which of the following types of genetic rearrangements or mutations was likely introduced by the mutagen? (A) Silent mutation (B) Missense mutation (C) Nonsense mutation (D) Duplication

Step-by-Step Solution

Answer

The most likely type of genetic rearrangement or mutation introduced by benzopyrene in this scenario is a \(Nonsense\) mutation, as it results in the formation of a stop codon, causing the protein to be shorter after translation.

Step 1: Option A: Silent Mutation

A silent mutation does not change the amino acid sequence of the protein. Instead, it changes the genetic code in a way that the codon still codes for the same amino acid, due to the redundancy in the genetic code. This would not result in the observed shorter protein in this scenario, so this is not the correct answer.

Step 2: Option B: Missense Mutation

A missense mutation involves a base substitution that results in a change in the amino acid specified by the codon. While this could change the structure or function of the protein, it would not make the protein shorter. Therefore, this option is not likely the cause.

Step 3: Option C: Nonsense Mutation

A nonsense mutation is a base substitution that results in the formation of a stop codon, which signals the end of translation. When a gene has a nonsense mutation, the protein produced could be shortened because translation stops prematurely. This would lead to the observed shorter protein in this scenario, so this is the correct answer.

Step 4: Option D: Duplication

Duplication involves the copying of a genomic region, resulting in multiple copies of a gene or other genomic elements. This type of genetic rearrangement would not likely result in a shorter protein being produced, so it is not likely the cause of the observed change. Given the analysis of each option, the most likely type of genetic rearrangement or mutation introduced by the mutagen is: (C) Nonsense mutation