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

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

Answer 2

Answer:

The substitution caused silent mutation which did not change the amino acid and hence, no effect on function of respective protein.

Explanation:

A mutation that does not cause change in the amino acid and hence no effect on the function of the protein is called as silent mutation. The substitution mutation in the gene for fur color was silent mutation and hence, did not affected the final resulting phenotype.

Example: Substitution of "U" for "C" at third position in genetic code UUU leads to new genetic code UUC. Since both UUU and UUC code for phenylalanine, the phenotype would remain unchanged.