Hey, you might wanna try something like this...

A B C
1 Gene1 Gene2 Unique?
2 red black 1
3 blue white 0
4 green red 0
5 yellow orange 1
6 purple yellow 0
7 pink taupe 0

In this example I've used the following calculation in the Unique column (just copy the formula down):
=COUNTIF($B$2:$B$7,A2)

If = 0, then unique to that list, if = 1, then not unique. You'd have to do this for both columns though...