I disagree with Neuronix on this one.
Genetics is an invaluable course. You do not need to take it before the MCAT, however a sound knowledge of genetics is critical for the changing face of medicine. As medicine becomes increasingly molecular, genetics is becoming indispensible.
Will you get Genetics in med school? Yes, of course. But, unlike other courses (e.g. anatomy), you'll cover it in greater detail in college.
Don't take Genetics to get a leg up on med school, because in the grand scheme of things, it'll be a small component of your premedical coursework. Take it because it will undoubtedly shape your career over the next few decades.
Get a liberal education, but don't miss out on Genetics.
Cheers,
doepug