Question

As per ABO blood grouping system, the blood group of father is $B^+$ , mother is $A^+$ and child is $O^+$. Their respective genotype can be
A. $I^B i/I^A i/ii$
B. $I^B I^B /I^A I^A /ii$
C. $ I^A I^B /iI^A /I^B i$
D. $I^A i/I^B i/I^A i$
E. $iI^B /iI^A /I^A I^B$
Choose the most appropriate answer from the options given below :

• A. A only
• B. B only
• C. C & B only
• D. D & E only

Answer 1

The Correct Option is A

The ABO blood group system is defined by red blood cell surface antigens, governed by the gene I with three alleles: $I^A$, $I^B$, and $i$. $I^A$ and $I^B$ are codominant, while $i$ is recessive.

Given the phenotypes:

• Father's blood group $B^+$: Possible genotypes are $I^B I^B$ or $I^B i$.
• Mother's blood group $A^+$: Possible genotypes are $I^A I^A$ or $I^A i$.
• Child's blood group $O^+$: Genotype must be $ii$, requiring two recessive alleles.

Evaluating each option:

• Option A: $I^B i/I^A i/ii$
  • Father: $I^B i$
  • Mother: $I^A i$
  • Child: $ii$
  • This is possible because $I^B i$ and $I^A i$ can produce an $ii$ offspring.
• Option B: $I^B I^B /I^A I^A /ii$
  • Father: $I^B I^B$
  • Mother: $I^A I^A$
  • Child: $ii$
  • This is impossible. Two homozygous dominant parents ($I^B I^B$ and $I^A I^A$) cannot produce an $ii$ child.
• Option C: $I^A I^B /iI^A /I^B i$
  • Incompatible genotypes and outcomes. Skipped due to lack of relevance to the parent-offspring relationship presented.
• Option D: $I^A i/I^B i/I^A i$
  • Incompatible genotypes as no $ii$ genotype is possible for an $O^+$ child.
• Option E: $iI^B /iI^A /I^A I^B$
  • Incompatible genotypes because an $I^A I^B$ child cannot have an $O^+$ blood group.

The sole viable genotype combination enabling an $O^+$ child is presented in Option A: $I^B i/I^A i/ii$.

Therefore, the correct answer is A only.