Answer:
- Frequency of recessive allele n for spider syndrome is 0.35.
This frequency can be designated q .
- Accordingi to hardy weinberg equilbirum p+ q = 1 , where p is
the frequency of the normal dominant N allele.
- p = 1 - 0.35 = 0.65
- p2 + 2pq + q2 =
1
- p2 is the frequency of NN genotype individuals
- 2pq is the frequency of heterzygotes Nn
- q2 is the frequency of nn genotype individuals
the
frequency of genotype are:
- NN = 0.65 x 0.65 = 0.4225
- Nn = 2 x 0.65 x 0.35 = 0.455
- nn = 0.35 x 0.35 = 0.1225
- lets assume the population consists of 1000 before
selection
- expected number of NN genotype = 1000 x 0.4225 = 422.5
- expected number of Nn genotype = 0.455 x 1000 = 455
- expected number of nn genotype = 0.1225 x 1000 = 122.5
- followimg selection all 122.5 nn genotype individuals would
die.
- Now the population will consist of 422.5 NN genotype and 455 Nn
genotype sheeps.
- allele frequency of N allele = number of NN sheeps x 2 + number
of Nn sheeps / total number of sheeps left x 2
Note:we are multiplying number of homozygous NN
sheeps by 2 because each sheep contains 2 N alleles.
Heterozygous sheeps contains only one N allele. The sheep
population is diploid and each sheeps contains 2 alleles of a
particulat gene
- allele frequency of N = 422.5 x 2 + 455 / ( 422.5 + 455) x 2 =
845 + 455 / 1755 = 0.74
- allele frequency of n = number of nn sheeps x 2 + number of Nn
sheeps / total number of sheeps after selection x 2 = 0 + 455 / (
422.5 + 455 ) x 2 = 455 / 1755 = 0.26
- NN genotype frequency = 0.74 x 0.74 =
0.55
- Nn genotype frequency = 2 x 0.74 x
0.26 = 0.38
- nn genotype frequency = 0.26 x 0.26 =
0.07
- The allelic frequency of N and n
after selection is 0.74 and 0.26
The
genotypic frequency of NN , Nn and nn after selection is 0.55, 0.38
and 0.07 respectively.
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