22.4 The spliceosome contains snRNAS Recognition across intron Recognition across exon Intron Exon Exon Intron E×on|ntro UACUAAC- A U UACUAAC-PyAC-G s site Branch 5 site Branch 3 site 5 sit site SR proteins SR pr ote ins E complex 12AF U1GUUACUAAG UACUAAC- ↓ GU UACUAAC-PAG GU A complex GU UACUAAC一PyAO igure 22 1 1 There may be multiple routes for initial 活大[ recognition of5cand3 splice sites.Figure 22.11 There may be multiple routes for initial recognition of 5￠ and 3￠ splice sites. 22.4 The spliceosome contains snRNAs