When a population has a gene with two alleles circulating, how many possible genotypes are there?
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Given:
Genotypes pp and pc, give pink coloration in 70 out of 350 conches.
Genotype cc, gives cream coloration in 280 out of 350 conches.
To find: the number of offspring in a population of 300 snails with pink coloration.
Method: Using punnett square and hardy wineberg equation to solve the problem.
Solution:
The Punnett square for the given data is shown in the image. Based on the given data, one can infer that the presence of 'p' allele hinders the expression of 'c' allele inspite of 'c' being the dominant allele. Thus we'll use the homogenous dominant 'cc' conches to find the frequency of the 'c' allele.
No. of conches with 'cc' genotype = 280
Frequency of 'cc' allele =
∴ c² = 0.8
c = √0.8 = 0.89
Since 'c' and 'p' alleles are in equilibrium,
p + c = 1
p = 1 - c = 1 - 0.89 = 0.11
∴ c = 0.89 and p = 0.11
Now, the number of heterogenous carriers will be,
Hence, no.of heterogenous carriers (pc),given by 2pc = 0.2
Now, the number of pink colored snails will be, p² + 2pc = 0.0121 + 0.2 = 0.21
Hence, any population size will have 21% of the snails in pink coloration.
The, 21% of a 300 sized population will be, = 63.
Hence, 63 snail offspring will be pink colored.