How many phenotypic 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 1: Understand the Genetic Basis of Blood Groups
Human blood groups are determined by the ABO blood group system, which is controlled by a single genetic locus. This locus has three alleles: IA, IB, and i (or I).

### Step 2: Identify Possible Genotypes
The combinations of these alleles can form various genotypes. The possible genotypes for the ABO blood group system are:
1. IA IA (homozygous for A)
2. IA i (heterozygous for A)
3. IB IB (homozygous for B)
4. IB i (heterozygous for B)
5. IA IB (heterozygous for AB)
6. ii (homozygous for O)

### Step 3: Determine Corresponding Phenotypes
From the identified genotypes, we can assign the corresponding phenotypes (blood groups):
1. IA IA → Blood Group A
2. IA i → Blood Group A
3. IB IB → Blood Group B
4. IB i → Blood Group B
5. IA IB → Blood Group AB
6. ii → Blood Group O

### Step 4: Count the Unique Phenotypic Classes
Now, we can summarize the unique phenotypic classes based on the genotypes:
- Blood Group A (from IA IA and IA i)
- Blood Group B (from IB IB and IB i)
- Blood Group AB (from IA IB)
- Blood Group O (from ii)

Thus, there are a total of **four phenotypic classes** for human blood groups: A, B, AB, and O.

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

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