A cross is set up between a female fly heterozygous for thre

A cross is set up between a female fly heterozygous for three X-linked genes and a male fly with recessive alleles on his X chromosome. The genes are: y+ (yellow body is recessive to black body), ct+ (cut wings is recessive to normal wings), and m+ (miniature wings is recessive to long wings). The following progeny are obtained: 30 yellow, miniature wings, uncut wings 33 black, long wings, cut wings 10 yellow, long wings, cut wings 12 black, miniature wings, uncut wings 8 black, miniature wings, cut wings 5 yellow, long wings, uncut wings 1 yellow, miniature wings, cut wings 1 wild-type (black with long, uncut wings) a) Which classes represent the non-crossovers? b) Which classes represent double crossovers? c) Which gene is in the middle? d) What is the correct phasing of the genes in the heterozygous female parent?

Solution

Answer=

number phenotypes type

30   yellow, miniature wings, uncut wings parental ( non crossover)

33 black, long wings ,cut wings Parental (noncrossover)

10 yellow, long wings, cut wings single crossover

12 black, miniature wings, uncut wings    single crossover

8 black, miniature wings, cut wings single crossover

5 yellow, long wings, uncut wings single crossover

1 yellow, miniature wings, cut wings Double crossover

1 wild-type (black with long, uncut wings) Double crossover

a) The classes which occurs more frequently represents non crossover i.e. parental type

i.e. yellow, miniature wings, uncut wings AND black, long wings, cut wings

b) classes which occurs least frequently represent double crossovers

yellow, miniature wings, cut wings AND wild-type (black with long, uncut wings) represent double crossover