Question

Inheritance of blood group is a condition of
1. Co-dominance
2. Incomplete dominance
3. Multiple allelism
4. Multiple gene

• A. 1, 2
• B. 2, 4
• C. 2, 3
• D. 1, 4
• E. 1, 3

Answer 1

Answer: (E)

1, 3

Incomplete dominance is the condition when the dominant allele is not completely dominant over the recessive resulting in a mixture of dominant-recessive phenotype in heterozygous condition. When a single trait is governed by more than one gene, it is said to be under control of multiple genes. Human blood group inheritance is the example of codominance and multiple alleles. It is governed by three alleles of gene "I", namely I${}^A$, I${}^B$ and I${}^O$. I${}^A$ and I${}^B$ show codominance while allele "I${}^O$" is recessive to both "I${}^A$" and "I${}^B$". This gives total six genotypes and four phenotypes : A (I${}^A$ I${}^A$ and I${}^A$ I${}^O$), B (I${}^B$ I${}^B$ and I${}^B$ I${}^O$) , AB (I${}^A$ I${}^B$) and O (I${}^O$ I${}^O$). Correct option is "E".