Question

The gene D controls wing shape in flies and has two alleles: D is wild-type and dominant, and d is recessive and causes flies to have downward pointed wings. The gene E controls eye development and also has two alleles: E is wild-type and dominant, and e is recessive and causes the flies to have small eyes. The two genes are located on the same chromosome. A true-breeding fly with wild-type wings and small eyes was crossed with a true-breeding fly with downward wings and wild-type eyes. All of the F1 progeny had a wild-type phenotype. The recombination frequency between the two genes is 20%. If an F1 individual was test crossed to a ddee fly, what percentage of the progeny would you expect to have the WT phenotype?

Answer 1

Answer:

10% of progeny would have wild type phenotype

Explanation:

True breeding fly with wild type wings and small eyes: De/De

True breeding fly with downward wings and wild type eyes: dE/dE

Cross between them :  De/De X dE/dE = De/dE ( F1 )

Recombination frequency = 20%

Next cross, De/dE X de/de =

De/de = parental = 40%

dE/de = parental = 40%

DE/de = recombinant = 10%

de/de = recombinant = 10%

The third genotype i.e. one of the recombinant genotypes will have the wild type makeup ( DE/de ) hence 10% of flies would have wild type phenotype.