Blood types are controlled by multiple alleles.
Human blood type is determined by codominant alleles.
Each person has two alleles for their blood type, one dominant and one recessive. Except for type AB blood where the alleles are co-dominant. The allele for O blood is always recessive when paired with either an A or B allele.
It's potentially 3. A,B,O. Not necessarily ALL of them though, I believe.
The ABO blood groups in humans are controlled by multiple alleles.
Multiple alleles
Blood type in humans is an example of multiple alleles.
Can B+ type blood be transfused into O type blood in humans?
Yes.
It can be an example of co-dominance, a seen in people with type AB blood.
Yes, Type O is the unmutated blood type, we all have a recessive gene for type O because it is the first blood type had by humans.
3
B) codominance