In Drosophila, a cross between a male and female from a mutant strain with plum-
ID: 12697 • Letter: I
Question
In Drosophila, a cross between a male and female from a mutant strain with plum-colored eyes yields 2/3 progeny with plum-colored eyes and 1/3 progeny with red (normal-colored) eyes. A cross between a male and female from a mutant strain with stubble (short) bristles yields 2/3 progeny with stubble bristles and 1/3 with normal length bristles. Both genes are autosomal and assort independently.Predict the ratio of progeny produced by a mating between two flies with plum-colored eyes and stubble bristles.
Give your answer as a ratio in the order plum eyes with stubble bristles:plum eyes with normal bristles:normal eyes with stubble bristles:normal eyes with normal bristles. Reduce the ratio to smallest numbers, e.g. 7:3:2:1.
Explanation / Answer
plum x plum => 2/3 plum : 1/3 red stubble x stubble => 2/3 stubble : 1/3 normal I assume plum (P) is dominant over red (p) and stubble (S) is dominant over normal (s); and these two genes are lethal dominance (PP and SS die before birth). P: plum stubble PpSs x plum stubble (PpSs) Gametes: (PS, Ps, pS, ps) x (PS, Ps, pS, ps) F1 (Punnet square) ------|--PS--|---Ps---|---pS---|--ps-- PS | lethal | lethal | lethal | PpSs Ps | lethal | lethal | PpSs | Ppss pS | lethal | PpSs | lethal | ppSs ps | PpSs | Ppss | ppSs | ppss Phenotypic ratio: 4 plum stubble : 2 plum normal : 2 red stubble : 1 red normal