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 x eeSS? Show your work.

Solution

cross between EEss and eeSS gives a F1 progeny of EeSs.

the gametes produced are ES Es eS es, the F2 progeny are

W-wildtype, L-long hair

phenotypic ratio is 13 wildtype: 3 long winged

	ES	Es	eS	es
ES	EESS/W	EESs/W	EeSS/W	EeSs/W
Es	EESS/W	EESs/W	EeSS/W	EeSs/W
eS	EESS/W	EESs/W	eeSS/L	eeSs/L
es	EESS/W	EESs/W	eeSs/L	EeSs/W