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In chickens, a flat single comb is a recessive trait, while the short, thick rose comb is dominant. In a particular population of chickens, 45 are homozygous for the dominant trait, 30 are heterozygous dominant, and 25 have the recessive trait. Which expression is the correct way to calculate the frequency of the recessive allele?

A. [tex]\frac{80}{100}[/tex]
B. [tex]\frac{80}{200}[/tex]
C. [tex]\frac{55}{100}[/tex]
D. [tex]\frac{55}{200}[/tex]
E. [tex]\frac{120}{200}[/tex]



Answer :

GinnyAnswer
Let's walk through the steps needed to calculate the frequency of the recessive allele given the population details.

1. Count the total number of chickens:
- Homozygous dominant: 45
- Heterozygous dominant: 30
- Recessive: 25
- Total chickens = 45 + 30 + 25 = 100

2. Calculate the total number of alleles in the population:
Each chicken has 2 alleles. Therefore, the total number of alleles = 2 total number of chickens = 2 100 = 200 alleles.

3. Calculate the number of recessive alleles:
- Each homozygous dominant chicken (45) has 0 recessive alleles.
- Each heterozygous dominant chicken (30) has 1 recessive allele.
- Each recessive chicken (25) has 2 recessive alleles.
- Total recessive alleles = (0 45) + (1 30) + (2 * 25) = 0 + 30 + 50 = 80 recessive alleles.

4. Calculate the frequency of the recessive allele:
The frequency of the recessive allele is given by the proportion of recessive alleles to the total number of alleles.
- Frequency of the recessive allele = [tex]\(\frac{\text{Number of recessive alleles}}{\text{Total number of alleles}} = \frac{80}{200}\)[/tex].

Thus, the correct expression to calculate the frequency of the recessive allele is:
[tex]\[ B. \frac{80}{200} \][/tex]

Therefore, the correct answer is (B) [tex]\(\frac{80}{200}\)[/tex].