Question

How might similarities and differences in genetic codes, or the proteins built as a result of these codes, be used to determine how closely related different species are?

Answer 1

Well, let's say it is 100 million years ago and you are the only biologist with a sequencing machine on Earth.

You sequence the DNA from an gene in an organism. Then 100 million years pass - some of that organism's descendents become one species (A) and the rest become a different species (B).

The key is that in both species A and species B, mutations have happened in the gene you sequenced. The mutations are random, so there is a good probability that they are different in the two species. The more time passes, the more mutations there are.

So by resequencing that gene from A and B and comparing how similar (or not) the sequences are, you can tell how long ago the species diverged from one another.

That's the science behind it.

Answer 2

thanks blues :)

Answer 3

No prob. ;)