How many phenotyic classes are found for human blood group in population ?

Options

A. 3
B. 4
C. 5
D. 6

Answer

To determine how many phenotypic classes are found for human blood groups in a population, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Blood Groups**:
- Human blood groups are classified into the ABO system, which is controlled by the gene known as 'i'.
- The gene 'i' has three alleles: IA, IB, and i (or IO).

2. **Identifying Allelic Combinations**:
- Since humans are diploid organisms, they have two alleles for the blood group gene.
- The possible combinations of these alleles can be:
- IAIA
- IAi (IAIO)
- IBIB
- IBi (IBIO)
- IAIB
- ii (IOIO)

3. **Determining Genotypes**:
- From the combinations listed, we can identify the genotypes:
- IAIA corresponds to blood group A
- IAi corresponds to blood group A
- IBIB corresponds to blood group B
- IBi corresponds to blood group B
- IAIB corresponds to blood group AB
- ii corresponds to blood group O

4. **Identifying Phenotypes**:
- Now we can categorize these genotypes into phenotypes:
- Blood group A (from IAIA and IAi)
- Blood group B (from IBIB and IBi)
- Blood group AB (from IAIB)
- Blood group O (from ii)

5. **Counting Phenotypic Classes**:
- Thus, we can see that there are four distinct phenotypic classes:
1. Blood group A
2. Blood group B
3. Blood group AB
4. Blood group O

6. **Conclusion**:
- Therefore, the total number of phenotypic classes for human blood groups in a population is **4**.

### Final Answer:
The number of phenotypic classes found for human blood groups in a population is **4**.

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