Question

Mrs. Watkins is examining the DNA sequences of a group of mice. He notices that in one of the mice, one nucleotide pair is substituted with another in the part of the DNA sequence that codes for fur color. However, despite the substitution the mouse still has the same fur color as the other mice. Why doesn't the substitution of the nucleotide change the physical trait.

The mouse has completely different DNA

The Substituted codons code for the same amino acid as the original nucleotide codon.

Substitutions in the nucleotides of a mouse's DNA NEVER affects their physical traits

DNA sequences don't determine the color of a mouse's fur.

Answer 1

The correct explanation for why the substitution of the nucleotide does not change the physical trait (fur color) in the mouse is:

**The substituted codons code for the same amino acid as the original nucleotide codon.**

This phenomenon is known as a "silent mutation" or "synonymous mutation," where a change in the nucleotide sequence does not result in a change in the amino acid sequence of the protein. Since the protein that governs fur color remains unchanged, the physical trait (fur color) also remains the same.