Question

Define codominance. Explain the concept of co-dominance by taking an example of AB blood group in humans.

Hint:

In incomplete dominance, the traits "blend" (like pink flowers), but in codominance, "both" traits show up clearly (like AB blood).

Answer 1

Step 1: Definition - Codominance is a phenomenon in which both the alleles of a gene pair in a heterozygote are fully expressed, resulting in an offspring with a phenotype that is neither dominant nor recessive.
Step 2: AB Blood Group Example - Human blood groups are controlled by the gene $I$, which has three alleles: $I^A$, $I^B$, and $i$. Alleles $I^A$ and $I^B$ are both dominant over $i$.
Step 3: Expression - When a person has the genotype $I^A I^B$, both alleles express their own types of sugars on the surface of red blood cells. This results in the AB blood group, showcasing codominance.