How is Drosophila male sex determination characterized?

The correct choice is based on a key aspect of Drosophila sex determination. In Drosophila, male sex determination is characterized by the presence of a specific splice variant of the doublesex (dsx) gene that leads to the formation of a functional male product. This process starts with the sex-lethal (Sxl) gene, which regulates splicing of the transformer (tra) gene. In males, the absence of the Sxl protein leads to the formation of a non-functional splice product of tra, which in turn influences the splicing of dsx.

The result of this regulated splicing pathway ensures that males receive a non-functional product of the tra gene that ultimately does not allow for the expression of female-specific Dsx protein variants, leading to the expression of male-specific characteristics. This genetic mechanism highlights the critical role of alternative splicing in sex determination processes in Drosophila.

Although some of the other concepts mentioned in the other choices relate to gene regulation and control mechanisms, they do not accurately depict the specific outcome of the splicing event for male sex determination, which fundamentally hinges on the production of the non-functional splice variant.