BIOL 200 Lecture Notes - Lecture 23: Exonic Splicing Enhancer, Alternative Splicing, U2Af2
Document Summary
Avrg exon: 150bp; avrg intron: > 0. 5 million bp! Marks where the 3" extremity is (3" splice site) Exonic splicing enhancers: helps the entire machinery find where the intron- exon boundaries are. Alternative splicing: enables complexity from only 30,000 genes. Hepatocyte fibronectin mrna does not -- eiiia & eiiib are spliced out. This gene is only on in early embryos of females. Later in development, it"s on in both (?) Only female embryos will make sex-lethal protein; male embryos do not. For females, the sex-lethal protein will sit down at 3" end of exon 2. & exon 3; exon 3 is spliced out (as an intron; skipped!) in females! For males, they have exon 3. they try to make a protein out of exon 3. But there"s a stop very early in exon 3. So the males screw up, can"t make any sex-lethal protein. Tra/tra2 binds to rbp1; they both bind exonic splicing enhancers in exon 4.
