CBSE 2025, Set 2

Question

A child with blood group A has a father with blood group B and a mother with blood group AB. Choose the option that gives the correct genotypes of father, mother and the child: A). Father: $I^Ai$, Mother: $I^Bi$, Child: $I^Ai$ B). Father: $I^AI^B$, Mother: $I^Ai$, Child: $I^AI^A$ C). Father: $I^Bi$, Mother: $I^AI^B$, Child: $I^Ai$ D). Father: $I^BI^B$, Mother: $I^AI^B$, Child: $I^AI^A$

Edvaya · Accepted Answer

The correct answer is Father: $I^Bi$, Mother: $I^AI^B$, Child: $I^Ai$. **SOLUTION** Let's break down the genetic possibilities: * **Mother:** Has Blood Group AB. Her genotype must be **$I^A I^B$**. * **Father:** Has Blood Group B. His genotype can be $I^B I^B$ or $I^B i$. * **Child:** Has Blood Group A. The child must have inherited the $I^A$ allele from the mother. To have blood group A, the other allele must be $i$ (making the child $I^A i$). If the child had inherited an $I^B$ from the father, the child would be AB. * Therefore, the father must carry the recessive $i$ allele to pass it on. The father's genotype is **$I^B i$**. * The child's genotype is **$I^A i$**. The correct combination is: Father: $I^B i$, Mother: $I^A I^B$, Child: $I^A i$.

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Biology > Reproduction And Genetics > Principles Of Inheritance And Variation

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