From the following blood types, determine which baby belongs to which parents? Also, give reasons for the same.
| i) Mrs. Kumar | Type A |
|---|---|
| ii) Mr. Kumar | Type A |
| iii) Mrs. Sharma | Type A |
| iv) Mr. Sharma | Type AB |
| v) Baby 1 | Type O |
| vi) Baby 2 | Type B |
For blood type, A & B are dominant alleles, & O is recessive to A & B. However, a person can have a phenotype of A (it looks like A type blood), but a genotype of AO (one An allele from one parent, an O allele from the other).
This seems to be what the Kumars have. They both have type A blood, however, they most likely both have the genotype of AO (because if one of them was just an AA, their babies would definitely be type A). There is a baby with type O blood, & since the Kumars do not have B alleles, they have the O baby.
If we use a Punnett square for the Kumars, we can get offspring with the genotypes AA, AO, AO or OO. AA & AO would have the phenotype of type A blood, while OO will be type O blood. (O is recessive to the A & B alleles). Type O is what their offspring have. Since neither parents have the B allele (because it would show up in the phenotype, if so like Mr. Sharma), they can definitely not pass on a B allele & have a baby with type B blood. Mrs. Sharma is type A, & Mr. Sharma is type AB. We must be thinking: well, Mrs. Sharma could have the genotype of AO, right? So their baby could type O. However, if we do a Punnett square, the possibilities are offspring with genotypes of AA, AB, AO or BO. Since O is recessive to the A & B alleles, there is NOWAY that the Sharmas baby can have type O blood.
Phenotype possibilities
Kumars’ offspring: 75% of type A blood, 25% of type O blood.
Sharma’s offspring: 50% of type A blood, 25% of type AB blood, 25% of type B blood.
Thus, Baby 1 (type O) belongs to the Kumars & Baby 2 (type B) belongs to the Sharma’s.