In Drosophila sex determination, the Sex-lethal ( Sxl ) and transformer ( tra an
ID: 79454 • Letter: I
Question
In Drosophila sex determination, the Sex-lethal (Sxl) and transformer (tra and tra-2) gene products undergo alternative splicing in males and females. Which of the following statements accurately describes the regulation of these genes?
These three genes are transcribed in females; they are not transcribed in males.
Each of these three genes autoregulates the splicing of its own pre-mRNA.
The male and female isoforms of these gene products are transcribed from different promoters.
The female isoforms of these gene products undergo alternative splicing; the male isoforms do not.
The male isoforms of these gene products include an additional exon that contains a premature stop codon.
Explanation / Answer
Answer: 5
Explanation-In males, the third exon is included which encodes a stop codon, causing a truncated form to be produced. In the female version, the presence of sex-lethal causes this exon to be missed out; the other seven amino acids are produced as a full peptide chain, again giving a difference between males and females.