If the frequency of a dominant phenotype in a stable population is 75%, the frequency of recessive allele in that population would be

Options

A. 0.375
B. 0.75
C. 0.094
D. 0.5

Explanation

To solve the question about the frequency of the recessive allele in a population where the frequency of the dominant phenotype is 75%, we can use the Hardy-Weinberg principle. Here’s a step-by-step solution:

### Step 1: Understand the Phenotype Frequencies
The question states that the frequency of the dominant phenotype is 75%. This means that 75% of the individuals in the population express the dominant trait.

### Step 2: Determine the Frequency of the Recessive Phenotype
Since the total frequency of all phenotypes must equal 1 (or 100%), we can calculate the frequency of the recessive phenotype:
- Frequency of recessive phenotype = 1 - Frequency of dominant phenotype
- Frequency of recessive phenotype = 1 - 0.75 = 0.25 (or 25%)

### Step 3: Relate Phenotype Frequencies to Genotype Frequencies
According to the Hardy-Weinberg principle, the frequency of the dominant phenotype (which includes both homozygous dominant and heterozygous individuals) can be expressed as:
- Frequency of dominant phenotype (p^2 + 2pq) = 0.75
- Frequency of recessive phenotype (q^2) = 0.25

Where:
- p = frequency of the dominant allele
- q = frequency of the recessive allele

### Step 4: Calculate the Frequency of the Recessive Allele
Since we know that the frequency of the recessive phenotype (q^2) is 0.25, we can find q by taking the square root:
- q = √(0.25) = 0.5

### Step 5: Conclusion
Thus, the frequency of the recessive allele (q) in the population is 0.5.

### Final Answer
The frequency of the recessive allele in that population would be **0.5**.

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