Draw a box. On the vertical side of the box write A and O
On the horizontal side write B and O
Take each letter and combine it with the two letters in the other plane and write them in the box.
AB AO OB OO and BA BO OA OO
Knowing that the A and B genes are dominant … you get the following children probabilities:
AO OA are A’s
OB BO are B’s
AB BA are AB’s
OO and OO are O’s
THE TWO PARENTS CAN PRODUCE all the blood types of the ABO SYSTEM.