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Unformatted text preview: er synthesis, the non-templated addition of extra ribonucleotides
(CCA) to some tRNAs. 22 BIO 1140 Unit 2-2: Transcription Pre-mRNA Processing
3. RNA Splicing:
Many mRNAs in eucaryotes (and a few in procaryotes) have an
intron/exon structure. Removal of introns is necessary prior to translation.
(Actually some non-coding RNAs have introns too!)
Introns: Non-protein-coding sequences in the pre-mRNA
Exons: Amino acid coding sequences in pre-mRNA
A complex of proteins and snRNAs carries out the splicing reactions.
This is the “Spliceosome”. . 23 BIO 1140 Unit 2-2: Transcription Pre-mRNA Processing
3. RNA Splicing: If a gene has several introns, in some cases “alternative splicing” will
results in different versions of mRNA can be produced.
In these mRNAs exons are joined in different combinations that can
be translated into different proteins with different functions.
More information can be stored in the DNA!
But are these different genes or just different proteins? 24 Fig. 13-7, p. 2...
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- Winter '07