In Drosophila, the dominant allele Cy (Curly) results in curly wings. The cross Cy/ x Cy/ (where represents the wildtype allele of Cy) results in a ratio of 2 curly : 1 wildtype F1 progeny. The cross between the curly F1 progeny also gives a ratio of 2 curly : 1 wildtype F2 progeny. How can this result best be explained

d

Explanation:

Using a Punnet square to represent the given information

The cross between Cy + and Cy + can be computed as:

            Cy                  +

Cy       Cy Cy               Cy +

+           Cy +                ++

From what we see above, it is above that the ratio of Curly to wildtype is in the ratio of 2:1

This illustrates that the genotype Cy Cy is lethal. This is explained when two curly F1 are crossed which resulted in the same ratio.

Hence, the inheritance of Cy/Cy is fatal.

the denominator has a very specific role.