Practice question

Major spliceosome, responsible for U2 type GT-AG introns comprising more than ninety-nine percent of introns, contains five abundant snRNAs U1, U2, U4, U5, U6 transcribed by RNA polymerase II, capped with trimethylguanosine and assembled with Sm core. U1 base pairs with five prime splice site, U2 binds branch point, tri-snRNP U4/U6.U5 enters. Minor spliceosome for AT-AC introns uses U11, U12, U4atac, U6atac, U5. Distinct sets explain inability of major spliceosome to recognize AT-AC consensus lacking GU but having AU at five prime and AC at three prime with highly conserved branch point.