Question

You are fascinated by the genetics of butterflies, and are especially intrigued by the fact that in butterflies, females are the heterogametic sex. You cross true-breeding yellow female butterflies with eyespots on their wings to true-breeding red males without eyespots. You know that the F1 progeny were all orange, but your assistant left the notes about presence or absence of eyespots out in the rain, and the data were lost. You decide to self the F1 to confirm your suspicion about the inheritance of color, and to see if you can figure out what is going on with the inheritance of eyespots. Your F2 progeny data are presented in the table below. yellow, spotted red, spotted orange, spotted yellow, no spots red, no spots orange, no spots 17 F2 males 16 F2 , 17 17 16 31 31 47 46 46 47 94 94

1) How is the trait of spots on wings inherited?

2) What proprotion of the F2 male butterflies are yellow?

3) How is the trait of spots on wings inherited ?

please thank you!

Answer 1

No spot is dominant over spotted phenotype. This is because of higher number of progenies with no spots in F2 generation. So, the trait of spots will follow inheritance of complete dominance.

Proportion of yellow male butterflies in F2 = number of yellow males / total number of males × 100 = 63/251 × 100 = 25.09%

Colour is inherited as incomplete dominance trait. The allele for red colour is incompletely dominant over allele for yellow colour. This is the reason some of the orange progenies are also seen.

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