Question

3. Consider two loci. One locus has two alleles, A1 and A2 at frequencies p = 0.3 and q = 0.7, respectively, and the other locus has two alleles, B1 and B2 at frequencies r = 0.4 and s = 0.6. (A) What are the possible genotypes of gametes made by organisms in this population? (B) What will be the frequencies of gametes produced by individuals in this population if the two loci are in gametic equilibrium (meaning that they are assorting completely independently)?

Answer 1

Sol. 3

(A)

All possible Genotypes of gametes made organisms of this population are

A_{​​​​​​1} B_{​​​​​​1} ,A_{​​​​​​2} B_{​​​​​​2} ,A_{​​​​​​1} B_{​​​​​​2} and A_{​​​​​​2} B_{​​​​​​1} .

(B)

Given, frequencies of alleles on the two loci are as follows:

• Frequency of allele A_{​​​​​​1} ,p=0.3
• Frequency of allele A_{​​​​​​2} ,q=0.7
• Frequency of allele B_{​​​​​​1} ,r=0.4
• Frequency of allele B_{​​​​​​2} ,s=0.6

So, frequencies of gametes produced by individuals in this population if the two loci are in genetic equilibrium can be calculated as:

• Frequency of gamete A_{​​​​​​1} B_{​​​​​​1} is (0.3×0.4)= 0.12
• Frequency of gamete A_{​​​​​​2} B_{​​​​​2} is (0.7×0.6)= 0.42
• Frequency of gamete A_{​​​​​​1}​​​ B_{​​​​​​2} is (0.3×0.6)= 0.18
• Frequency of gamete A_{​​​​​​2} B_{​​​​​​1}​​​ is (0.7×0.4)= 0.28

Since, the two loci are in genetic equilibrium so, the sum of the frequencies must be equal to one which is clearly visible here as follows:

Sum of frequencies of the gametes= (0.12+0.42+0.18+0.28)

= 1.00