Question

Below is a partial DNA sequence (the original sequence with no mutations); only the coding strand is shown.

Assume the sequence is transcribed and translated from left to right with the reading frame as indicated.

5' - | GGC | GTG | GTA | TTA | GCG | - 3'

This sequence represents a single mutation.

Mutation #1: 5' - | GGC | GCG | GTA | TTA | GCG | - 3'
Complete these sentences about this mutated DNA sequence

This mutant DNA sequence is the result of a __________ (transition or transversion?) mutation. The effect of this base substitution on the amino acid sequence results in a ___________ (nonsense, silent, or missense?) mutation.

Answer 1

The mutant DNA sequence represents a transversion mutation, leading to a missense mutation, which results in the substitution of Valine for Alanine in the amino acid sequence.

Step-by-step explanation:

The mutant DNA sequence 5' - | GGC | GCG | GTA | TTA | GCG | - 3' compared to the original sequence 5' - | GGC | GTG | GTA | TTA | GCG | - 3' is the result of a transversion mutation. This occurs when a purine (A or G) is replaced with a pyrimidine (C or T) or vice versa. In this case, T has been replaced with C. The effect of this base substitution on the amino acid sequence results in a missense mutation. Since the codon GTG (coding for Valine) is changed to GCG (coding for Alanine), the change in a single nucleotide results in the incorporation of a different amino acid into the developing peptide chain.