MBB331_Week10-Fall-2011

T branch site deleted branch branch site targets the

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: f bands (>300 bands expected if 7 introns removed randomly) introns • Splicing occurs by specific order Splicing of events…. Intron 5 or 6 are the first removed, then the other is the second intron removed, intron 3 is never lost during one of the first 3 steps…. steps…. • The order of intron removal for The ovomucoid is: intron 5/6 ---> 7/4 ---> 2 ---> 3/1 ---> • But… other order pathways exist Lewin Genes VII 2000 Oxford University Press 70 NUCLEAR mRNA PRECURSOR SPLICING NUCLEAR mRNA PRECURSOR SPLICING • (1) Cut at 5´splice site (1) separating left exon from right intron-exon RNA intron-exon • (2) Right intron-exon forms (2) lariat linking 5´ end to 2´-OH lariat on target A within intron ---> 5 on ´-2´ branch site formed ´-2´ branch • (3) Cut made at 3´splice site, (3) intron released, & right exon joined to left exon joined -branch site marks 3´ splice site, and is located 18-40 nt upstream of 3´ splice site upstream Lewin Genes VII 2000 Oxford University Press 71 SPLICING SITES SPLICING • yeast branch site consensus: UACUAAC • Consensus branch site not well conserved in higher Consensus eukaryotes: but contains invariant “A” eukaryotes: • Relaxed constraints in higher eukaryotes ---> cryptic Relaxed branch sites used when w.t. branch site deleted branch • Branch site targets the nearest 3´ splice site for joining Branch with the 5´ splice site with 72 TRANSESTERIFICATION TRANSESTERIFICATIO...
View Full Document

This note was uploaded on 03/26/2014 for the course MBB 321 taught by Professor Davidson during the Spring '11 term at Simon Fraser.

Ask a homework question - tutors are online