In flies a recessive mutation in the E gene e causes wings t

In flies, a recessive mutation in the E gene (e) causes wings to be extended longer than wild type. A mutation in a second unlinked recessive mutation in the S gene has no phenotype on its own, but the homozygous ss mutation causes flies with the ee genotype to have a wild type phenotype. What is phenotypic ratio expected in the F2 progeny of a cross between EEss times eeSS? Show your work.

Solution

Gamates

ES

Es

eS

es

ES

EESS

EESs

EeSS

EeSs

Es

EESs

EEss

EeSs

Eess

eS

EeSS

EeSs

eeSS

eeSs

es

EeSs

Eess

eeSs

eess

This an example for homozygous recessive interaction or recessive epistasis. In this type of epistasis the recessive allele at one locus with mask the expression of other gene locus. In this type if one of the gene is dominant it shows dominant character. Recessive character is shown only when both alleles are recessive. In this the possible gamates from EEss X eeSS are ES, Es, eS and es. When crossed the above punnett square. In this Punnett square the alleles that are bold and underlined shows dominant character and other one\'s are recessive character. The phenotypic ratio is 9:7 ie, is 9 are wild type wings and 7 are extended type of wings.

Gamates ES Es eS es ES EESS EESs EeSS EeSs Es EESs EEss EeSs Eess eS EeSS EeSs eeSS eeSs es EeSs Eess eeSs eess