You are investigating two traits in fruit flies controlled by one gene each. The

Question

You are investigating two traits in fruit flies controlled by one gene each. The b gene controls for body color, while the rgene controls for body sculpture. After crossing rugose black flies with smooth brown flies, you obtain an F1 generation of 100% smooth black flies. What are the dominant alleles? (1 pt) What should be the genotype of the tester individual be to perform a dihybrid test cross? (2 pt) After running a dihybrid test cross, you find 1000 offspring with the following phenotypes: Observed 396 102 98 404 1000 Expected Black, rugose Plack, smooth Brown, rugose Brown, smooth Fill in the expected column with the expected number of offspring in each class of phenotypes. (1 pt) What phenotype classes represent the recombinant phenotypes? (1 pts each) Calculate the relative genetic distance between the genes controlling for body color and body sculpting. (1 pt)

Explanation / Answer

Answer.

1).

Black(B) color is dominant over brown (b) color.

Smooth (R) is dominant over rugose(r).

2). Genotype of the tested individual to be performed test cross is BbRr.

3).

BbRr x bbrr -----Test cross

Expected genotypes

4). Recombinant phenotypes are as follows.

Black, smooth

Brown, rugose

5). Recombination frequency = ( 102+98/1000)100= 20

Recombination frequency (%) = Distance between the genes ( map units)

The distance between the two genes= 20 m.u.

br BR BbRr ( 250)--black, smooth Br Bbrr (250)--black, rugose bR bbRr (250)---brown, smooth br bbrr(250)---brown, rugose

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