Can a 0- and a a- make a a?

Answer 1

you need to make a punnett square.

you know that the first person has A+ blood, so their side of the punnett square is either A+ A+, A+ O-, A- O+, A+ O+

you know the second person has either B- B- or B- O-

then you put them into punnett squares:

in order to have type O blood, you must have 2 o's so we will only look at the possible O combinations. Also to have negative, you must have no positive Rh in the blood, so we only need to look at the pairs that contain an O-

A+ O-

B- AB+ BO-

O- AO+ OO-

OO- can really be written as O- because the dominant antigen takes over and they are the same, so,

A+ and B- blood can make O- blood, but only under certain conditions.

So, YES!