Question

Out o f the three alleles of gene $I$, the sugar polymers on the plasma membrane of $RBCs$ is controlled by how many alleles?

• A. All three
• B. Two
• C. One
• D. O

Answer 1

Answer: (B)

The plasma membrane of the red blood cells has sugar polymers that protrude from its surface and the kind of sugar is controlled by '$I$' gene. It has three alleles $I^A,I^B$ and $i$. Out of these only two alleles $I^A$ and $I^B$ produce a slightly different form of the sugar, while allele $i$ does not produce any sugar. Because humans are diploid organisms, each person possesses any two of the three $I$ gene alleles. $I^A$ and $I^B$ are completely dominant over $i$.