Say a population of fish exhibit two slightly different phenotypes; long fins vs

Question

Say a population of fish exhibit two slightly different phenotypes; long fins vs. short fins. The B allele is dominant = long, the b allele is recessive = short. If there are 160 fish in the population, 60 are homozygous dominant calculate the following: How many individuals are homozygous for the B allele? What is the frequency of individuals that are homozygous for the B allele? What is the frequency of the B allele? What is the frequency of the b allele? What is the frequency of individuals that are homozygous for the b allele? How many individuals are homozygous for the b allele? What is the frequency of individuals that are heterozygous? How many individuals are heterozygous? How many fish have long fins? How many fish have short fins?

Explanation / Answer

According to Hardy-Weinberg equilibrium allelic frequency is always one

So B+b =1

Genotype frequency is given by B2+ b2+2Bb =1

Given that there are 160 fish in the pond out of which 60 are homozygous dominant

So the frequency of homozygous dominant will be 60/160 = 0.375.

B2 = 0.375

B = 0.61

B+b =1

So b = 1-B

= 1-0.61

b = 0.39

The frequency of homozygous recessive will be b2 = 0.39*0.39 = 0.155

Frequency of heterozygous will be 2*B*b = 2*0.61*0.39 = 0.47

Number of the individual having homozygous recessive gene will be 0.155*160 = 25

NUmber of individual having heterozygous condition i.e. Bb allele will be 0.47*160 = 75.

How many individuals are homozygous for the B allele = 60

What is the frequency of individuals that are homozygous for the B allele = 0.375

What is the frequency of the B allele = 0.61

What is the frequency of the b allele = 0.39

What is the frequency of individuals that are homozygous for the b allele 0.155

How many individuals are homozygous for the b allele = 25

What is the frequency of individuals that are heterozygous= 0.47

How many individuals are heterozygous = 75

How many fish have long fins fish having genotype BB and Bb will have long fins so total number will be 60+75 = 135

How many fish have short fins 25

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