hey, just clarification on the blood thing ( I know I didn't post it, but it's something I actually understand!lol)  
A=one chemical. B=another chemical. O=lack of either chemical And AB= both chemicals
+=has a different chemical -=does not have that chemical.
If you receive blood that has a chemical that you don't, then your body won't accept it. Actually, that can be a problem in some pregnancies, when the baby has a blood type that is significantly different than the mother. 
So, obviously, you can only pass on chemicals that you have. My dad is 0+. That would mean that I would have to be positive, no matter what my mother's blood type was. My mom has A+. That means that my blood type has to be A+ as well, because O is lack of a chemical, and thus gets covered up. O- can give to anybody, as it has no offending chemicals. AB+ can receive anything, because it already has all of the chemicals. 
So if both of your parents were O- lets say, and you were AB+, you are a mailman's kid. 
I used to know what all of the chemicals were called, but I don't anymore.