Question

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

Answer 1

dna replication is not error free, the enzymes incharge have an error once in let say 1 million bases. these changes are within somatic cells as well as ovi and sperms (meaning it is carried through generations).
counting the number of mutations thus serves as a clock, in which the "time unit" is defined by th error rate of replication.
for this to hold truth no selective pressure must take place as it may weed out problematic sequence changes, therefore silent mutations, in which no selection is anticipated are important