Question

Child with blood group ‘O’ has ‘B' group father and ‘A’ group mother. the father and mother have a genotype of :
1. ii × I^AI^A
2. I^Ai × I^Bi
3. ii × I^BI^B
4. I^AI^A × I^BI^B

Answer 1

Correct Answer - Option 2 : I^Ai × I^Bi

Concept-

• The blood of human beings differs in certain aspects though it appears to be similar.
• Various types of grouping of blood have been done.
• Two such groupings - the ABO and Rh - are widely used all over the world. 
• ABO grouping is based on the presence or absence of two surface antigens (chemicals that can induce an immune response) on the RBCs namely A and B.
• Similarly, the plasma of different individuals contains two natural antibodies (proteins produced in response to antigens).
• The distribution of antigens and antibodies in the four groups of blood, A, B, AB, and O. 

Explanation-

• ii - The blood group is O(child).
• To have a child with an O blood group, both parents should have at least one copy of i allele.
• So the parents are heterozygous.
• I^Bi - The blood group of the father.
• I^Ai - The blood group of the mother.

Therefore the father and mother have a genotype of I^Ai × I^Bi.

• ABO blood groups are determined by three alleles - I^A, I^B, I^O.
• I^A  = Dominant
• I^B = Dominant
• I^O = Recessive

Allele from Parent 1	Allele from Parent 2	Genotype of offspring	Blood types of offspring
IA	IA	IA IA	A
IA	IO	IA IO	A
IA	IB	IA IB	AB
IB	IB	IB IB	B
IB	IO	IB IO	B
IO	IO	IO  IO	O