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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]$\frac{10}{300}$[/tex]

C. [tex]$\frac{15}{100}$[/tex]

D. [tex]$\frac{35}{200}$[/tex]

E. [tex]$\frac{120}{100}$[/tex]



Answer :

GinnyAnswer
Let's walk through the process of determining the frequency of the recessive allele based on the given chicken population data.

1. Determine the total number of chickens:
We have:
- Homozygous dominant (RR) chickens: 45
- Heterozygous dominant (Rr) chickens: 30
- Recessive (rr) chickens: 25

The total number of chickens is:
[tex]\[ 45 + 30 + 25 = 100 \][/tex]

2. Calculate the total number of alleles in the population:
Each chicken has 2 alleles (since they are diploid organisms). Therefore, the total number of alleles is:
[tex]\[ 2 \times 100 = 200 \][/tex]

3. Count the number of recessive alleles (r):
- Each recessive (rr) chicken contributes 2 recessive alleles:
[tex]\[ 25 \times 2 = 50 \][/tex]
- Each heterozygous dominant (Rr) chicken contributes 1 recessive allele:
[tex]\[ 30 \times 1 = 30 \][/tex]

Adding these together, the total number of recessive alleles is:
[tex]\[ 50 + 30 = 80 \][/tex]

4. Calculate the frequency of the recessive allele (q):
The frequency of the recessive allele can be found by dividing the total number of recessive alleles by the total number of alleles in the population:
[tex]\[ \frac{80}{200} = 0.4 \][/tex]

Given this information, the correct expression for calculating the frequency of the recessive allele from the provided options is:
[tex]\[ \text{Option D:} \quad \frac{80}{200} \][/tex]

Therefore, the correct answer is:
[tex]\[ \boxed{\frac{80}{200}} \][/tex]

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