Question

I am writing a report for a lab involving experimenting on drosophila melanogaster to study their inheritance pattern. The goal of the lab was to predict the genotypes of the P cross by observing the phenotypes and their ratios in the F1 and F2 generation. Our F2 generation contained wildtype flies, white mutation, ebony mutation, and white/ebony double mutants. I am having trouble interpreting the results of the Chi square tested conducted on our flies.

Our total Chi square values are much higher than the critical value and I narrowed it down through a troubleshooting chi square test based on sex. The problem seems to be coming from the WT and white males. Our vials contained way more wildtype males than expected and not as many nearly as many white males as we expected. I am not sure how to explain why this happened. Does it have something to do with the white mutation being sex linked, the WT being more dominant, maybe we did something wrong? What genetic laws are demonstrated here?

Phenotype	Observed	Expected	O-E	(O-E)^2	(O-E)^2/E
WT F	19	20	1	1	0.05
White F	19	20	1	1	0.05
Ebony F	6	7	-1	1	0.14
E /W F	8	7	1	1	0.14
Total					0.38
WT M	32	20	12	144	7.2
White M	9	20	-11	121	6.1
Ebony M	10	7	3	9	1.29
W/E M	6	6	-1	1	0.14
Total					14.73

Answer 1

you have calculated the chi squre pefectly.

your final answer is 0.83 for female

your final answer is 14.37. for male

let us consider the degree of freedom 3 at chance 0.05.

the chi squre is = 7.815

from comparing to female our null hypothesis is accepted but when we come to male it is rejected.

its ok ,now let us focus another veiw of cross .

let us consider that these genes ar present on the Xchromosome , and here is a chance of crrossing over and recombination during gamete formation.

in female drossophilla there is XX dose and in Male drossophilla there is only single X and Y dose .

when after fertilization female progeny having two XX out of that the character which one is dominant will express in that female. But in male the thing is not like that the gene [allele] present on single X chromosome will express itself [it may be recessive or dominat].

now we consider the chances of fertilization of gametes of different combination.

In nature which gamete [X wild or mutant] will fertilize with which gamete we cant predict .

the observed result is a chance of type of gametic fussion . As male is having only one X so expressed the came X gentic combination.

That I predict from your experiment.