Question

Dr. stevens 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 with the correct dna sequence.why doesn't the substitution of nucleotides in the mouse change its phenotype, or physical characteristics?

Answer 1

Out of the following given choices;

A.      The mouse has a completely different DNA sequence than the other mice.

B.       The substituted nucleotide has the same directions as the original nucleotide.

C.      Substitutions in the nucleotides of a mouse's DNA never affect their phenotypes.

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

The answer is B. Most probably, the nucleotide substitution did not translate to a change in the amino acid sequence in the translated protein. As you may be aware, most amino acids are coded by more than one codon. For example, Leucine is coded for by CTT, CTC, CTA, CTG, TTA, TTG. Therefore, a substitution, that causes a change to either one of the sequences will not change the amino acid.