Question

A man of blood group A marries a woman of AB blood group AB. Which type of progeny would indicate that man is heterozygous A?
A. AB
B. A
C. O
D. B

Answer 1

Hint: Alleles present in gamete or cell can be recognized by inheritance law or by inheritance chart during the segregation of alleles and the formation of progeny takes place. The blood groups consist of alleles I which are named as ${I^A},{I^B},{I^O}$. Heterozygous means having non similar alleles paired together in a cell.

Complete answer:
Inheritance is a process in which one individual passes his/her traits to the other individual via sexual or asexual reproduction.
According to the law of segregation, every allele segregates from its pair and acts as a single domain which later mates with other alleles forming a different mixture of pairs having different genotypes and phenotypes.
In blood, according to the situation, man have blood group A (Heterozygous) and Female have blood group AB so the possible progeny genotype are –
> Blood group A - ${I^A}{I^O}$
> Blood group AB - ${I^A}{I^B}$
Progeny can be of alleles combination - ${I^{AA}},{I^{AO}},{I^{AB}},{I^{BO}}$
Whereas if the man is Homozygous it will have the alleles combination of A ( ${I^A}{I^A}$ ) when it mate with the women having AB ( ${I^A}{I^B}$ ) blood group the gamete formation will have progeny with alleles ${I^{AA}}{I^{AB}}$ with 50 $\% $ recombination rate.

Hence, if the man is heterozygous A, it will form progeny with blood group B otherwise in homozygous A, only AB and A blood group progeny are formed.

Note: Alleles distribute themselves with 25 $\% $ of recombination traits if the parent gamete is heterozygous whereas recombination with 50 $\% $ can be seen in traits with a homozygous parent. In blood codominance the phenomenon of ABO blood group can be seen.