Question

Study the pedigree chart given below, which shows the pattern of blood group inheritance in a family.

1. State the genotypes of the following:
   1. Parents
   2. The individual ‘X’ in the second generation.
2. State the possible blood group(s) of the individual ‘Y’ in the 3^rd generation.

Answer 1

i. a. Parents (Generation I): Parents have blood groups A and B, and they have a child with blood group O.

For an O (ii) child, both parents must contribute ‘i’.

∴ Father (A) = I^Ai, Mother (B) = I^Bi

b. Individual ‘X’ (Generation II): The AB male has genotype I^AI^B and their child is A.

So the child must be I^AI^A or I^Ai. Since father already provides I^A, X must give either I^A or i.

∴ X can be I^Ai (blood group A) or ii (blood group O).

ii. Mother has blood group O, so her genotype is ii. Father has blood group A, so his genotype can be I^AI^A or I^Ai.

If the father is I^AI^A, then all offspring will be I^Ai and the blood group will be A.

If the father is I^Ai, then the offspring can be I^Ai or ii, giving blood groups A or O.

Therefore, Y can have blood group A or O.