Question

Explain the mechanism of sex determination in insects like Drosophila and Grasshopper.

Answer 1

Hint: The sex determination in humans is done by XY chromosomes while in Drosophila and Grasshopper it is done by XY and XO mechanism respectively.

Complete answer:
Sex is a biological system that determines the development of sexual characteristics in an organism. The most organism requires two individuals to create offspring using sexual reproduction. Sex determination is mostly genetic with males and females having different genes to determine their sexuality.

The sex determination mechanism in the case of Drosophila is XX and XY system. Although it is similar to humans in Drosophila, the Y chromosome does not determine the maleness as in the case of humans. The sex in Drosophila is simply determined by the ratio of the number of X chromosomes to that of the number of sets of autosomes. The sex determination is achieved by a balance of female determinants on the X chromosome (X) and make determinants on the autosomes (A), the Y chromosome does not have a role in sex determination. This is known as the Genic balance theory.

In the case of Grasshopper, a different sex determination mechanism system XX and XO are used. In this, the females have two copies of X chromosomes (XX) while males have only one (XO). The O denotes the absence of the second chromosome, there is no Y chromosome. The presence of a single X chromosome determines the maleness in an individual.

Note: Sex determination was discovered in the mealworm for the first time by the American geneticist Nettie Stevens in 1903. Generally, it is found that the sex of an animal’s offspring depends on whether a sex chromosome is present in the male gamete or not. Males are the determiners of sex in the offspring because they are heterochromatic having different types of sex chromosomes.