MBB331_Week10-Fall-2011

Genes introns 67 howareexonscorrectly

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Unformatted text preview: nce is Further size discrepancy between nuclear gene and RNA product: average size of hnRNA (heterogenous nuclear) bigger than mRNA • hnRNA is unstable and has greater hnRNA sequence complexity sequence 65 RNA SPLICING SYSTEMS RNA SPLICING SYSTEMS • (1) Nuclear intron splicing in higher eukaryotes: -short consensus sequences mark exon-intron -short boundaries and splicing executed by spliceosome spliceosome • (2) Self-splicing introns: -some introns can splice themselves without aid of -some proteins proteins -two classes: Group I & Group II introns (group II -two introns related to nuclear introns) introns • (3) Yeast tRNA splicing: -cleavage & ligation reactions separate (unlike -cleavage other splicing where breakage & reunion of RNA coordinated) coordinated) 66 GT-AG RULE FOR NUCLEAR INTRONS GT-AG Lewin Genes VII 2000 Oxford University Press • Splice sites are sites of RNA breakage & reunion Splice and are at exon-intron boundaries: 5´ GT splice site donor & 3´ AG splice site acceptor site • GT-AG rule applies to all eukaryote nuclear GT-AG genes but not to mitochondrial or chloroplast introns or yeast tRNA genes introns 67 • • • HOW ARE EXONS CORRECTLY HOW ARE EXONS CORRECTLY JOINED? Simple splice sites often Simple many kb’s distant - how do correct splice donors & acceptors f...
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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.

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