Question

Explain what it means for a section of DNA to be considered a molecular clock. Be sure to discuss the importance of neutral mutations in this measure of time.

Answer 1

Neutral mutations are mutations which do not affect the function of whatever protein the gene codes for or whatever purpose the non-coding DNA serves. In some cases they do not change the sequence of the protein (i.e., the mutated DNA still codes for the same amino acid as the unmutated DNA) and in other cases where the DNA now codes for a different amino acid, that new amino acid doesn't affect the structure or function of the protein.

The key is that neutral mutations do not affect the fitness of the organism or its ability to pass on its DNA.

The other key is that mutations are random and, in pieces of DNA used as molecular clocks, occur at a slow, constant rate. That constant rate is the same for the species being compared. By comparing the sequences of DNA from different species for how many mutations have occurred, it is possible to estimate how long ago the species diverged (i.e., how closely they are related.)

Hope this is helpful.