What is Sex-switch gene?

Explanation

(i) A gene, sex-lethal (SxL) located on the X chromosome, in Drosophila directs female development.
(ii) This gene has two states of activity. When it is 'on' it directs female development and when it is 'off' maleness ensures.
(iii) Other genes located on the X chromosome and autosomes regulates sex switch gene.
(iv) However, the Y chromosome of Drosophila is required for male fertility.