Expert: Dana Krempels, Ph.D. - 8/21/2007

Question
I can't think of the name of this, but I remember hearing that there is a way to tell how close two species are related to each other by checking how close the number of their (genes?) are to matching each other. Could you please tell me what this is called? Thanks a lot!

Answer
Dear J,

Are you referring to DNA sequencing?  One way to determine how closely related two species are is to sequence a particular gene or DNA sequence in both species, and see how much of the DNA they share in common.

When this is done, the gene sequence must be chosen carefully, to avoid using a sequence that mutates rapidly, or is often changed in some other way.  For this reason, mitochondrial DNA sequencing is often considered the most reliable, since mitochondrial DNA doesn't recombine between generations, and stays mostly the same from mother to child.  This is quite different from the DNA in the nucleus, which is very different from parent to child.

Is that what you were thinking?  Hope that helps!

Dana