Ok, so if your father or mother is O type, can you be an AB type?
The answer is no, since O type have to be homozygous recessive, meaning that A person with O type blood cannot have the gene for type A or type B.
for you to be an AB type, you must receive an A from mother and B from father, or the other way round. However, since father does not contain A or B gene ( if he does, he would not be an O type), this can never happen
