Question

If one child in the family has blood group AB and another child has O, what will be the genotypes of their parents?
A. $$I^A{I}^B$$ and $$I^o{I}^o$$
B. $$I^A{I}^A$$ and $$I^B{I}^B$$
C. $$I^A{I}^o$$ and $$I^B{I}^o$$
D. $$I^A{I}^B$$ and $$I^A{I}^B$$

Answer 1

Hint: The type of human blood is determined by codominant alleles. An allele is one of the different types of genetic material that is found in our DNA at a specific position on a particular chromosome. There are three distinct blood group alleles known as $$I^A$$ , $$I^B$$, and I. For convenience, these alleles can be named A (for $$I^A$$), B (for $$I^B$$), and O (for I).

Complete Answer:
- As each of us inherits one blood type allele from our biological mother and one from our biological father, each of us has two ABO blood type alleles. A definition of the allele pair in our DNA is called the genotype.
- As there are three separate alleles, there are a total of six distinct genotypes in the human ABO genetic locus. Various potential genotypes are AA, AO, BB, BO, AB, and OO. A blood test is used to assess if the characteristics of A and/or B are present in a blood sample. It is not possible to ascertain the exact genotype of either type A or type B blood test results.
- If anyone has type A blood, they must have at least one copy of the A allele, but they may have two copies. Its genotype is either AA or AO.Additionally, someone who is type B blood can have either a BB or a BO genotype. A type AB or type O blood test is more informative.
- Somebody with blood type AB must have both the A and B alleles. The genotype has to be AB. Someone with type O blood does not have either the A or the B allele. The genotype has to be OO.
- Each biological parent shall donate one of their two ABO alleles to their infant. A mother with a blood type O may only transfer an O allele to her son or daughter. A father with a blood type AB could transfer either an A or a B allele to his son or daughter. This couple may have children of either type A (O from mother and A from father) or type B (O from mother and B from father).

Mother’s Blood Type	Possible Mother's Genotype	Father’s Blood Type	Possible Father’s Genotype	Possible Child Blood Type
A	AA, AO	A	AA, AO	A, O
A	AA, AO	AB	AB	A, AB, B
A	AA, AO	B	BB, BO	A, AB, B, O
A	AA, AO	O	OO	A, O

Mother’s Blood Type	Possible Mother's Genotype	Father’s Blood Type	Possible Father’s Genotype	Possible Child Blood Type
AB	AB	A	AA, AO	A, AB, B
AB	AB	AB	AB	A, AB, B
AB	AB	B	BB, BO	A, AB, B
AB	AB	O	OO	A, B

Mother’s Blood Type	Possible Mother's Genotype	Father’s Blood Type	Possible Father’s Genotype	Possible Child Blood Type
B	BB, BO	A	AA, AO	A, AB, B, O
B	BB, BO	AB	AB	A, AB, B
B	BB, BO	B	BB, BO	B, O
B	BB, BO	O	OO	B, O

Mother’s Blood Type	Possible Mother's Genotype	Father’s Blood Type	Possible Father’s Genotype	Possible Child Blood Type
O	OO	A	AA, AO	A, O
O	OO	AB	AB	A, B
O	OO	B	BB, BO	B, O
O	OO	O	OO	O

The correct Answer is option (C)$$I^A{I}^o$$ and $$I^B{I}^o$$.

Note: It should be obvious from this discussion that the blood type is not a very successful paternity test. In certain cases , it is possible to obtain unmistakable details, i.e. the type AB male can not father the type O infant. In most cases, however, the results are uncertain. If it is important to ascertain the paternity of a child, there is currently a very sensitive DNA test available that can confirm paternity for more than 99.99 per cent or remove anyone as a biological father with utter certainty.