Question

ABO blood grouping is controlled by gene I which has three alleles and show Co-dominance. There are six genotypes. How many phenotypes in all are possible?

• A. Five
• B. Three
• C. Four
• D. Six+

Answer 1

The correct option is C

Four

The correct option is option C.

Explanation of the correct option:

Option C:

1. A single type of blood group is controlled by a pair of genes.
2. There is a total of 3 types of alleles, of which ${\mathrm{I}}^{\mathrm{A}}$ ${\mathrm{I}}^{\mathrm{B}}$ are dominant alleles whereas ${\mathrm{I}}^{\mathrm{o}}$is a recessive allele.
3. When the genotype is ${\mathrm{I}}^{\mathrm{A}}$${\mathrm{I}}^{\mathrm{A}}$ or${\mathrm{I}}^{\mathrm{A}}$${\mathrm{I}}^{\mathrm{o}}$, the phenotypic blood group is A.
4. When the genotype is ${\mathrm{I}}^{\mathrm{B}}$${\mathrm{I}}^{\mathrm{B}}$ or${\mathrm{I}}^{\mathrm{B}}$${\mathrm{I}}^{\mathrm{o}}$, the phenotypic blood group is B.
5. When the genotype is${\mathrm{I}}^{\mathrm{A}}$${\mathrm{I}}^{\mathrm{B}}$, the phenotypic blood group is AB.
6. When the genotype is${\mathrm{I}}^{\mathrm{o}}$${\mathrm{I}}^{\mathrm{o}}$, the phenotypic blood group is O.
7. Therefore, there are a total of 4 possible types of phenotypic expressions for the gene that controls the human ABO type of blood group.

Final answer: ABO blood grouping is controlled by gene I which has three alleles and show Co-dominance. There are six genotypes and Four phenotypes are possible.