Question

In heterozygous condition, both the alleles express in

• A. Colour blindness
• B. $AB$ blood group
• C. $Rh$ factor
• D. $A$ and $B$ blood types

Answer 1

Answer: (B)

• The gene $(I)$ has three alleles $I^A,I^B$ and $i$ The alleles $I^A$ and $I^B$ produce a slightly different form of the sugar while allele $i$ doesn’t 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 $i$, in other words when $I^A$ and $i$ are present only $I^A$ expresses (because $i$ does not produce any sugar), and when $I^B$ and $i$ are present $I^B$ expresses.
• But when $I^A$ and $I^B$ are present together they both ex press their own types of sugars: this is because of co dominance. Hence red blood cells have both $A$ and $B$ types of sugars.