I. Introduction to Sex Determination in Drosophila

Drosophila is commonly known as fruit flies. It is a model organism widely used in genetic and developmental biology research. The sex determination of Drosophila is done by the presence of a single pair of sex chromosomes, known as X and Y.

II. Chromosomal Sex Determination

• The presence of an X chromosome results in the development of a female, while the presence of a Y chromosome results in the development of a male.
• The sex determination process is initiated during the formation of the primary spermatocyte, where one of the two X chromosomes is randomly inactivated in the female cells.

III. Genetic Control of Sex Determination

• The master switch gene for sex determination in Drosophila is the fruitless (fru) gene, located on the Y chromosome.
• The fru gene encodes a transcription factor that controls the expression of other genes involved in the development of male-specific traits.
• The doublesex (dsx) gene, located on the autosomes, controls the development of both male and female traits, and its expression is regulated by the fru gene.

IV. Dosage Compensation

• Drosophila females have two copies of the X chromosome, while males have only one.
• To compensate for this difference in dosage, the X chromosome in females is inactivated through a process known as X-chromosome inactivation, where one of the two X chromosomes is randomly chosen and inactivated in each cell.

V. Conclusion

• The sex of Drosophila is determined by the presence of a single pair of sex chromosomes, X and Y.
• The master switch gene for sex determination in Drosophila is the fruitless (fru) gene, located on the Y chromosome and the doublesex (dsx) gene, located on the autosomes.
• Dosage compensation is achieved through X-chromosome inactivation in female cells, which ensures that the expression of X-linked genes is equal between sexes.