Question

In a cross with sweet pea (Lathyrus odoratus, which is related to the garden pea Pisum sativum, which Mendel studied), William Bateson (1913, Mendel’s Principles of Heredity. Cambridge: Cambridge University Press, p. 154) provided data for the F2 progeny from a dihybrid experiment for axil color and male fertility. (An axil is where a leaf is connected to the stem.) The gene for male sterility in this case is nuclear, not cytoplasmic. One parent had dark axils and was male fertile, and the other parent had light axils and was male sterile. The F2 progeny phenotypes were as follows:

Dark axils, male fertile 627

Light axils, male sterile 214

Dark axils, male sterile 27

Light axils, male fertile 17

Test the hypothesis that axil color and male fertility assort independently. What is your conclusion?

1. Reject
2. Do not reject

Answer 1

•Answer :- We know that according to the Mendel’s law of independent assortment, the dihybrid phenotypic ratio is 9:3:3:1. Let us compare the observed value is feet in that ratio [+/-] or not . If the observed values are in fitted in that proportion, we can accept that this cross is assort independently.

•Total progeny are = 627+214+27+17 = 885.

•Dark axils, male fertile = 9/ 16 then ?/885

Let us solve the problem = 9X885/ 16 = 497.81

It means our expected number of progeny should be 497.81 but our observed value is 627, it proves that it is not the 9th portion of 885.

•Light axils, male sterile = 3X885/ 16 = 165.93 .

It means our expected number of progeny should be 165.93 but our observed value is 214, it proves that it is not the 3rd portion of 885.

•Dark axils, male sterile = 3X885/ 16 = 165.93 .

It means our expected number of progeny should be 165.93 but our observed value is 27, it proves that it is not the 3rd portion of 885.

•Light axils, male fertile = 1 X 885/ 16 = 55.31

It means our expected number of progeny should be 55.31 but our observed value is 17 , It proves that it is not the 1th portion of 885.

From above calculation and results we can reject the hypothesis that axil color and male fertility assort independently