Final answer:
The sex determination system employed by Drosophila is known as the X-Y system, where females are XX and males are XY. This system is characterized by males being the heterogamous sex. Nettie Stevens's contributions solidified the understanding of the XY sex-determination system in scientific literature.
Step-by-step explanation:
The sex determination system used by Drosophila is the X-Y system. This means that Drosophila males have XY chromosomes, whereas females have XX chromosomes. In the context of Drosophila, males are said to be hemizygous because they possess only one allele for any X-linked characteristic.
Mammalian sex determination, which is also based on the X and Y chromosomes, similarly designates XX as female and XY as male. However, unlike some organisms that utilize the Z-W system, where females are the heterogamous sex (ZW) and males the homogamous sex (ZZ), the XY sex-determination system is characterized by males being the heterogamous sex.
Notably, pioneering scientist Nettie Stevens played a crucial role in understanding chromosomal sex determination by observing the chromosomal differences in mealworm cells, which led to the XY system's scientific acceptance. Drosophila's genetics have been a model for studying inheritance, including sex-linked traits.