One such RNA produced by the W chromosome, named “Fem” is the precursor of an RNA that silences the Masc gene. The Masc gene produces a protein causes the insect to express male features. A male silkworm with two Z chromosomes (ZZ) produces the Masc proteins and has male features. A female silkworm has a W chromosome that produces Fem and silences the Masc gene on the Z chromosome. A female produces very little Masc protein and has female features. Comparisons of sex determination in different species leads to a deeper understanding of the sex determination process in all species.
Read More: A single female-specific piRNA is the primary determiner of sex in the silkworm. Takashi Kiuchi, Hikaru Koga, Munetaka Kawamoto, Keisuke Shoji, Hiroki Sakai, Yuji Arai, Genki Ishihara, Shinpei Kawaoka, Sumio Sugano, Toru Shimada, Yutaka Suzuki, Masataka G. Suzuki & Susumu Katsuma. 2014. Nature 509: 633–636