Question

When two genes from two different people are sequenced and aligned, it is discovered that there are multiple sequence differences in the coding segment DNA level. However, when the proteins formed by the genes have their amino acids sequenced, there is no difference observed between the two. What is the most likely explanation for this observation?

(A) The mutations are repaired at the mRNA level after transcription has occurred, but before translation.
(B) RNA processing removes the different segments from the mRNA molecules of each person prior to translation.
(C) The mutations lie at locations where they don't affect protein sequence due to degeneracy of the genetic code.
(D) Mutations at the DNA level are not reflected in proteins produced.
(E) The mutations are corrected at the protein level after translation has occurred.

Answer 1

The existence of silent mutations due to the degeneracy of the genetic code explains why sequence differences in DNA may not lead to differences in protein sequences, as multiple codons can encode the same amino acid.

Step-by-step explanation:

The reason why there are multiple sequence differences in the coding segment DNA level but no observed differences in the protein sequence is likely due to the degeneracy of the genetic code. This means that multiple codons can code for the same amino acid. Thus, even though the DNA sequences of the two genes are different, the changes do not alter the amino acids encoded because the mutations fall at codons that result in the same amino acid — these are known as silent mutations.

Furthermore, considering the central dogma of molecular biology, the process of translation at the ribosome entails the reading of the mRNA sequence and the addition of the correct amino acids to form a polypeptide chain. If the silent mutations do not cause a change in the amino acids, the function and structure of the resulting protein will remain unchanged.