In medical genetics and blood transfusion compatibility, an individual with blood group AB… — JAMB UTME

In medical genetics and blood transfusion compatibility, an individual with blood group AB expresses both A and B antigens on their red blood cells. Which of the following best explains the genetic relationship between the $I^A$ and $I^B$ alleles?

The $I^A$ and $I^B$ alleles are codominant, allowing both antigens to be fully expressed.Answer
B
The $I^A$ allele is completely dominant over the recessive $I^B$ allele.
C
The $I^A$ and $I^B$ alleles undergo incomplete dominance to produce a blended trait.
D
The trait is sex-linked and expressed only on the X chromosome.

Answer

The

I^A

and

I^B

alleles display codominance, meaning both alleles are fully and independently expressed in individuals with blood group AB.

The correct option identifies codominance as the inheritance pattern where both

I^A

and

I^B

alleles are expressed equally and simultaneously in blood group AB individuals.

Step-by-Step Solution

Identify the genotype associated with blood group AB.

An individual with blood group AB possesses the heterozygous genotype

I^A I^B

Each parent contributes one allele (

I^A

I^B

) to the offspring.

Analyze how the alleles manifest in the phenotype.

Both antigen A and antigen B are present on the membrane of red blood cells.

When two different alleles are both expressed in a heterozygous organism, the genetic phenomenon is called codominance.

Key Concept

Codominance in ABO Blood Groups

Estimated Time:45s

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