Question

$ABO$ blood groups in human beings are controlled by the gene $I$. has three alleles - $I^A$, $I^B$ and $i$. Since there are three different alleles, six different genotypes are possible. How many phenotypes can occur ?

• A. three
• B. one
• C. four
• D. two.

Answer 1

Answer: (C)

In human beings $ABO$ blood groups are controlled by gene $I$ which has three alleles $I^A$, $I^B$ and $I$. The six possible genotypes are $I^A{I}^A$, $I^A{I}^B$, $I^{A}i$, $I^B{I}^B$, $I^{B}i$ and $ii$. The phenotypes which occur by these genotypes are $A(I^A{I}^A$, $I^{A}i)$, $B(I^B{I}^B$, $I^{B}i)$, $AB(I^A{I}^B)$ and $O(ii)$.