Question

If parent blood group A and AB, then which is not possible blood group in progeny?

• A. A
• B. AB
• C. B
• D. O

Hint:

For O blood type to occur in progeny, both parents must carry the O allele. If either parent has blood group A or AB, O cannot be inherited.

Answer 1

The Correct Option is D

In genetics, blood groups are determined by the alleles for the ABO blood group system. The alleles involved are A, B, and O. The possible combinations of these alleles define the blood group of an individual:

• A blood group: Can be genotype AA or AO.
• AB blood group: Has genotype AB.
• B blood group: Can be genotype BB or BO.
• O blood group: Has genotype OO.

When considering the potential blood types of progeny from parents with blood types A (either AA or AO) and AB, the following combinations are possible:

• If the parent with blood group A has genotype AA: The offspring can inherit either an A or an A allele from this parent.
• If the parent with blood group A has genotype AO: The offspring can inherit either an A or an O allele from this parent.
• The parent with blood group AB can pass on either an A or a B allele to the offspring.

The possible allele combinations for the progeny are:

• From AA parent:

  Parent A Allele	AB Parent Allele	Progeny Blood Group
  A	A	A
  A	B	AB

• From AO parent:

  Parent A Allele	AB Parent Allele	Progeny Blood Group
  A	A	A
  A	B	AB
  O	A	A
  O	B	B

From the above possible progeny blood groups, note that blood group O (genotype OO) is not achievable since there is no combination of alleles that can produce the OO genotype. Thus, blood group O is not possible in the progeny.