Human blood type is controlled by three alleles (A B. O). O is recessive and A and B
are co-dominant. A person must receive two O alleles for them to have type o blood.
If a person receives an A allele and a B allele, their blood type is type AB.
7.
A biology student is surprised and shocked to learn that although both parents
are blood type A, she is blood type 0. Is it possible that this student's parents
are both the true biological parents? If so, what must the parent genotypes be?
(Show the cross)

Yes, it is possible that this student's parents are both the true biological parents.

Their genotype must be heterozygous for the blood type A (AO).

Explanation: Each blood type is controlled by two alleles. A and B are dominant while O is recessive. For two parents that have blood type A to have a child with a blood type O, the both of them are heterozygous for blood type A, this means that each of them has one A dominant allele and one O recessive allele. Their genotype can be represented as AO. The child with blood type O is inherited one O recessive allele from each parent, that is she is homozygous for the blood type O. AO x AO = AA, AO, AO and OO.

AA and AO will manifest as blood type A while OO will manifest as blood type O.

See the attached punnet square for more information.

format change of dna.