Consider a hypothetical fish whose scale color is controlled by one gene with tw

Question

Consider a hypothetical fish whose scale color is controlled by one gene with two alleles. The gene is inherited in an incomplete dominance pattern. In a wild population of 1000 of these fish, there are 625 with blue scales and genotype SBSB, 175 with green scales and genotype SBSY, and 200 with yellow scales and genotype SYS 1. What is the allele frequency of the SD gene and the SY gene? 2. What is the genotype frequency observed in this population for blue fish, for green fish, and for yellow fish? 3. What is the genotype frequency expected if the population follows Hardy Weinburg equilibrium for the blue, the green, and the yellow fish 4. Explain why this fish population is, or is not in Hardy Weinburg equilibrium. If it is not in Hardy Weinburg equilibrium, what type of selection is likely occurring? Reply Subject (hidden) Author (hidden) This post cannot be viewed by you, probably because you have not posted in the discussion, the

Explanation / Answer

1) Calculate the expected genotypic frequencies:

SBSB (p2) = 625/100

= 0.625

p =0.790

So,

q=1-p

1- 0.790 = 0.21

Allele frequency of SB gene = 0.790

Allele frequency of SY gene = 0.21

2) Observed genotypic frequency

Fr blue fish

= 625/1000*100

= 62%

Green fish

= 175/1000*100

= 17.5%

Yellow fish

= 200/1000*100

= 20%

3) Calculate genotype frequency for blue fish using Hardy-Weinberg principle

p2 = 0.792

= 0.62 or 62%

Genotype frequency for green fish = 2pq

= 2*0.79*0.21

= 0.33 or 33%

Genotype frequency for yellow fish

= q2 = 0.212

= 0.04 or 4%

4) The above results are indicating that the population is not following Hardy-Weinberg equilibrium, because of the change in allele frequencies. In the given case, the selection is most likely directional.

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