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

Is this supposed to be an essay question?

By a 'molecular clock', the question is referring to how DNA naturally mutates over time as a predictable rate. Both mitochondrial and nuclear DNA can be used to 'date' how long ago two organisms or codes were identical, by calculating how much time it took for their codes to diverge to what is actually read.

For a simplified example, take the following 3 codes:
1) AATCG
2) ATTCG
3) TATCC

from 1 to 2 there is only 1 difference, while from 1 to 3 there are 2 differences. From this, we could (as a simple example) deduce that 1 and 3 diverged longer ago compared to when 1 and 2 diverged, because it took more time for 1 and 3 to have mutated to be 2 bases different while 1 and 2 only had the time to mutate to 1 base difference. (Note that this is a very simplified example)