Biology 2581B Lecture Notes - Lecture 18: Exonic Splicing Enhancer, Alternative Splicing, Exon
2 May 2020
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Document Summary
Sex-lethal protein is encoded by the sex-lethal gene and transcribed from a promoter present only in female embryos. The gene is shut off early in development. In males, under influence of the absence of early sxl protein, exon 2 of the late sex lethal pre-mrna is spliced to exon 3 to produce an mrna that contains a stop codon early in the sequence. As a result, male embryos produce no functional sxl protein either early or late in development. In females, sxl bind to an intronic splicing silencer, resulting in splicing of exon 2 to 4 and skipping exon 3. As a result, a functional sex-lethal mrna is produced, which reinforces its own expression: transformer (tra) protein: encoded by the transformer gene. Sxl protein regulates alternative splicing of the pre-mrna. In male embryos (no sxl) exon 1 is spliced into exon 2, which contains a stop codon that prevents synthesis of a functional protein.
