In: Biology
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
1) Which traits are dominant? 2) Do axil color and male fertility assort independently?
Ans: The dominant traits are Dark axils and Male fertile because the frequency of dark axils, male fertile classes is maximum compared to other classes.
The traits axil color and male fertility do not assort independently.
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
Total: 885
So, the assumed hypothesis either 1:1:1:1 or 9:3:3:1
If the hypotesis is 1:1:1:1, the expected phenotypes of each classe is 221.25
If the hypotesis is 9:3:3:1, the expected phenotypes of each classes are 497.81, 165.94, 165.94 and 55.31.
According to the deviation between observed and expected value, The hypothesis 9:3:3:1 is good fit
The calculated Chi-square value 44.94 is much higher than the table value 7.8 at 3 DF, the deviation between observed and expeced values are not good fit. Therefore, the assumed hypothesis 9:3:3:1 is rejected. So, The traits axil color and male fertility do not assort independently. There is a possibility of linkage.