Question

In flower beetles, pygmy (py) is recessive to normal size (py⁺), and red color (r) is recessive to brown (r⁺). A beetle heterozygous for these characteristics was test crossed to a beetle homozygous for pygmy and red. The progeny phenotypes from this testcross are shown below.

                                                py⁺   r⁺      180

                                                py⁺   r         22

                                                py     r⁺        19

                                                py     r       191

                                                Total          412

What is the frequency of recombination between these two genes?

      

Carry out a series of chi-square tests to determine if these genes are assorting independently. What does your chi-square value and associated probability indicate about whether these genes are linked?

Answer 1

The frequency of recombination is calculated by (recombinant/total) ×100

{(22+19) /412}×100=9.95 centiMorgan.

Hence the recombination frequency between two genes is 9.95%

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Null hypothesis: Two genes are assorted independently.

Then the expected number of each individual is (1/4) ×412=103

Please look in the image for chi square test:

Hence these two genes are not assorted independently.

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