I took Genetics once and due to a few reasons, including immaturity and working full-time, I ended up with an F thanks to not attending class and being too late to withdrawal.
Anywho, I am taking the online Genetics course through UC Berkley and it is exactly the same amount of credits and material.
Don't do online science classes that normally require a lab (O-Chem, Gen Bio, etc). However, since there are some science courses that rarely have a lab go ahead and take those online if you wish. The material is the material regardless of where you learn it.
Best of luck