As you can see
here, 7.015 doesn't seem be offered this year.
Furthermore, from the same link, you will find that 7.012 (the Fall course) is supposed to be the one with emphasis on genetic approaches. If I recall correctly, 7.015 focuses more on human biology, not genetics.
And hey, if you're crazy about genetics, maybe you should try to pass out of 7.012 and start in 7.03.