Choose the correct option with respect to the genetic makeup of the ABO blood grouping system in humans.

Options

A. 4 Alleles, 4 phenotype and 6 genotype
B. 3 Alleles, 6 phenotype and 4 genotypes
C. 4 Alleles, 6 phenotype and 4 genotypes
D. 3 Alleles, 4 phenotypes and 6 genotypes

Answer

To solve the question regarding the genetic makeup of the ABO blood grouping system in humans, we will analyze the information provided about the alleles and their combinations.

### Step-by-Step Solution:

1. **Understanding ABO Blood Groups**: The ABO blood grouping system consists of four main blood types: A, B, AB, and O. These blood types are determined by the presence of specific antigens on the surface of red blood cells.

2. **Identifying the Alleles**: The ABO blood groups are associated with three alleles:
- IA (which produces A antigens)
- IB (which produces B antigens)
- i (which does not produce any antigens)

3. **Dominance and Recessiveness**:
- IA and IB are both dominant alleles.
- The allele i is recessive.

4. **Genotypes for Each Blood Type**:
- **Type A**: Can be either homozygous (IAIA) or heterozygous (IAi).
- **Type B**: Can be either homozygous (IBIB) or heterozygous (IBi).
- **Type AB**: Only genotype is (IAIB) since both alleles are co-dominant.
- **Type O**: Only genotype is (ii) since it is recessive.

5. **Counting the Genotypes**:
- For blood type A: 2 genotypes (IAIA, IAi)
- For blood type B: 2 genotypes (IBIB, IBi)
- For blood type AB: 1 genotype (IAIB)
- For blood type O: 1 genotype (ii)
- Total genotypes = 2 (A) + 2 (B) + 1 (AB) + 1 (O) = 6 genotypes

6. **Conclusion**:
- There are three alleles (IA, IB, i), four phenotypes (A, B, AB, O), and six genotypes. Therefore, the correct answer to the question is that there are three alleles, four phenotypes, and six genotypes.

### Final Answer:
The correct option is: **Three alleles, four phenotypes, and six genotypes.**

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