Question

You are studying two traits in fruit flies: wing shape and eye color. Wings can be either bent or straight. Eyes can be either red or yellow. Straight-winged, yellow-eyed female X bent-winged, red-eyed male gave: 41 bent yellow males 38 bent red females 38 straight yellow males 43 straight red females an F1 bent-winged, red-eyed female X an F1 bent-winged, yellow-eyed male gave: 31 bent red females 10 straight red females 28 bent yellow females 11 straight yellow females 32 bent red males 9 straight red males 29 bent yellow males 10 straight yellow males Explain these results and give the genotypes of the parents in each of the crosses.

Answer 1

Answer:

From the observation, It can be seen that the bent-winged genotype is dominant, while the straight-winged genotype is recessive. Also, for the eye colour, the traits are found on only the X chromosome. This causes the males to inherit their eye colour from their mother, since females are the source of the single X chromosomes in males (XY- male). However, the females inherit their eye colour from their father's X-chromosome. Thus, it can be determined that the eye colour, in this instance, has a cross gender mode of inheritance due to its placement on the X-chromosome.  

Parent phenotype

Take: Bent-wing (B), Straight wing (s), Red eye (R) Yellow eye (Y)

Prime generation parent

Female (Straight-wing, Yellow eye)- s s   Y   (ss- homozygous recessive trait)

Male (Bent-wing, Red eye)- B s   R         (Bs- Heterozygous dominant trait)

1st generation Parent (F1)

Female (Bent-wing, Red eye)- B s     R

Male (Bent-wing, Yellow eye)- B s     Y