Question

Choose the correct statement with respect to Morgan's monohybrid experiment with eye colour of Drosophila, from the ones given below.

• A. Red eyed flies and white eyed flies appeared in the ratio of 3:1 in the $F_1$ generation
• B. White eyed females appeared in the $F_1$ generation indicating the presence of eye colour gene on the X chromosome.
• C. In the $F_2$ generation, female and male flies with red eyes were in the ratio of 2:1.
• D. The presence of white eyed female in the $F_2$ generation indicated the presence of eye colour gene on the X chromosome.

Answer 1

The correct option is C In the $F_2$ generation, female and male flies with red eyes were in the ratio of 2:1.

The monohybrid cross conducted by Morgan on Drosophila in which he had considered the gene for eye colour for experimental purposes, is shown below:

In the $F_2$ generation, red eyes and white eyes were in the ratio of 3:1. But another interesting fact was that there were only red eyed females and no white eyed females. In males, half of them were red eyed and the other half were white eyed. So, if we consider only the red eyed flies, females and males were in the ratio of 2:1.

In the $F_1$ generation, there were only red eyed flies (both males and females). There were no white eyed flies.