Genetic make-up is when you see someone who has one astounding feature and nothing else (such as a great ass but a flat chest and a butterface.) It's God's way of making it up to a person for screwing them in every other way.
God: "Hey, sorry about the flat chest, bad skin, and no brains. Here's an amazing ass. It's my genetic make-up to you."
God: "Yeah, I made you tall, thin, and socially awkward. I'll make it up to you. Here's a 10 inch crank."
ejaculating on a sexual partner's facial region.
I gave this chick some genetic makeup after some great head.
I asked this girl if she wanted some of my genetic makeup.