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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
To calculate the frequency of the recessive allele in this population of chickens, let's follow the genetic principles and systematically go through each step.

1. Determine the total number of alleles in the population:
- Each chicken has 2 alleles.
- The total number of chickens = [tex]\( 45 + 30 + 25 = 100 \)[/tex].

Therefore, the total number of alleles = [tex]\( 100 \times 2 = 200 \)[/tex].

2. Count the number of recessive alleles:
- Homozygous dominant chickens have 0 recessive alleles since they have both dominant alleles: [tex]\( 0 \times 45 = 0 \)[/tex].
- Heterozygous dominant chickens have 1 recessive allele each: [tex]\( 1 \times 30 = 30 \)[/tex].
- Recessive chickens have 2 recessive alleles each: [tex]\( 2 \times 25 = 50 \)[/tex].

Therefore, the total number of recessive alleles = [tex]\( 0 + 30 + 50 = 80 \)[/tex].

3. Calculate the frequency of the recessive allele:
- The frequency of the recessive allele is the ratio of the number of recessive alleles to the total number of alleles.

Hence, the frequency of the recessive allele is given by:
[tex]\[ \text{Frequency of recessive allele} = \frac{\text{Number of recessive alleles}}{\text{Total number of alleles}} = \frac{80}{200} \][/tex]

Given the step-by-step calculations above, the correct expression to calculate the frequency of the recessive allele is:

[tex]\[ \boxed{\frac{80}{200}} \][/tex]

Therefore, the correct answer is:

B. [tex]\(\frac{80}{200}\)[/tex]

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