A cross is performed between an ebony female fly with wild-type eyes and a male

Question

A cross is performed between an ebony female fly with wild-type eyes and a male fly with wild-type body color and sepia (brown) eyes (s) male fly. Ebony (e) and sepia (s) are recessive traits. All of the F1 offspring have the wild-type phenotypes.

1) What are the genotypes of the parental and F1 flies?

When the F1 offspring were crossed, the following results are obtained:

48 wild-type body color and eyes

26 ebony body color, wild-type eyes

24 wild-type body color, sepia eyes

2 ebony body color, sepia eyes

2) Examine the ratios of F1 phenotypes. Is this expected for traits that are not linked?

3) What is the recombinant genotype?

4) What is the frequency of recombination?

5) Does the recombination frequency you just calculated in the previous question estimate map distance directly?

Explanation / Answer

Parental:   Male Wild type body colour with Sepia eye X Female Ebony body colour with wild type Eye

Genotype:                               EEss                            X                     eeSS

Gametess:                               E , s                                                     e, S

F1 Generation:                                               EeSs EeSs EeSs EeSs

No, this is not expected for traits that are independent; the expected Traits would be 56 Wild type for both that is body colour and eye colour

19 would be Sepia eye with wild type body colour and 19 would be ebony body colour with wild type eye colour and 6 would be sepia eye colour with ebony body colour

The recombinant genotype would be EeSs, eeSS EEss

The frequency for recombinant will be 50 Percentage

Yes the calculated recombinant frequency will estimate map distance directly because

A recombinant frequency significantly less than 50 percent shows that the genes are linked. A recombinant frequency of 50 percent generally means that the genes are unlinked on separate chromosomes.

Map units = % recombination One map unit: the distance between gene pairs for which one product of meiosis out of 100 is recombinant. Map units usually, but not always proportional to physical distance. 1 mu = 1% recombination = 1cM (centimorgan)

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