Question

The function of some cyclin-dependent protein kinases (CDKs) has been remarkably conserved in evolution. Indeed, coding sequence for the human protein Cdc2 is able to substitute for the CDC28 gene in S. cerevisae and allow the yeast cell to grow and mate essentially normally. The following sequence near the NH2-end of the molecule is identical in both proteins: Gly-Glu-Gly-Thr-Tyr-Gly-Val-Val-Tyr-Lys-Ala. Does this mean that nucleotide sequences of the two genes coding for this region of the polypeptide are also identical? Explain your answer.

Answer 1

Does this mean that nucleotide sequences of the two genes coding for this region of the polypeptide are also identical?

No.

There are lot of possibilities that DNA sequence varies between human Cdc2 and CDC28 of S. cerevisae.

This is because of the redundant nature of genetic code, i.e., a single amino acid can be coded by more than one codons.

For example, leucine is coded by UUA, UUG, CUU, CUC, CUA, CUG.

Therefore, there is a possibility of variation in DNA sequence, even though protein sequence is same.