A presumed dihybrid female in Drosophila, B / b ; F / f is test- crossed with a

Question

A presumed dihybrid female in Drosophila, B/b ; F/f is test- crossed with a b/b;f/f male . (B black body;b brown body; F forked bristles; f unforked bristles.) The results are

Black, forked 260

Black, unforked 190

Brown, forked 180

Brown, unforked 270

Determine if these results fit the hypothesis that B and F assort independently. Show your work.

b.If the results are not consistent with the hypothesis that B and F assort independently, answer the following questions:

a. Which gametes would be parental gametes?

b. Which gametes would be recombinant gametes?

c. calculate the genetic distance between B and F.

Explanation / Answer

1. If these results fit the hypothesis that B and F assort independently. Show your work.

answer ; It can be seen in the through the chis square test . the hypothesis of the tested is dihybrid with idependently assorting genes and all that progeny are equally viable ,the expected values would be that phenotypes occur with equal frequency . there are 4 phenotypes so the degree of freedom is 3 , expected progeny is 263.

X2 = [ observed -expected ]2 / expected .

   = [ 260-263+ 190-263+ 180-263+270-263]2 / 263 = the value is 0.08 , so the genes are assoting independently .

b. 1.what would be the parental gamates ;

BF and bf are parental gamates

2. which gamates would be recombinants ;

Bf ,bF are recombinants

3. caluculating the genetic distance betwen the B and F ;

answer ; map distance = number of recombinants /total number of offsprings *100 = 370 /530 *100 = 69.8 cM

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