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lecture09 - Biology 172 Lecture 9 Wednesday Todays Outline...

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Lecture 9: Wednesday, May 26, 2010 Biology 172 Today’s Outline Announcements RNA Processing - cap, tail, splicing Translation - Overview - The Genetic Code - tRNA Structure/Function - Ribosomes Tomorrow’s Discussion: Central Dogma Quiz on Lectures 8 and 9
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RNA Processing - prokaryotes use RNA immediately in translation - eukaryotes “process” RNA before it is used
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RNA Processing Events in Eukaryotes - addition of “cap” to 5’ end of RNA - addition of poly A “tail” to 3’ end of RNA A modified guanine nucleotide added to the 5 end 50 to 250 adenine nucleotides added to the 3 end Protein-coding segment Polyadenylation signal Poly-A tail 3 UTR Stop codon Start codon 5 Cap 5 UTR AAUAAA AAA…AAA TRANSCRIPTION RNA PROCESSING DNA Pre-mRNA mRNA TRANSLATION Ribosome Polypeptide G P P P 5 3
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RNA Processing Events in Eukaryotes - addition of “cap” to 5’ end of RNA - addition of poly A “tail” to 3’ end of RNA - RNA splicing - removal of introns…. portions of the RNA not used in translation - conducted by spliceosome (RNA/protein complex) Figure 16-7a Primary RNA transcript DNA Promoter Intron 1 Intron 2 Exon 1 Exon 2 Exon 3 Spliced transcript 3 5 5 3 5 3
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Figure 16-7b snRNPs ARE THE EDITORS . Primary RNA snRNPs Exon 1 Exon 2 Intron Spliceosome 3 3 5 5 1. Several snRNPs and proteins assemble to form a spliceosome . An A (adenine) reacts with the 5’ end of the intron. A A snRNPs = snurps ” = small nuclear ribo- nucleoproteins = complexes of proteins and small RNAs
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Figure 16-7b Excised intron snRNPs ARE THE EDITORS . Exon 1 Exon 2 Mature mRNA 5 5 5 5 3 3 3 2 . The primary transcript (pre-mRNA) is processed in the spliceosome, which is made up of snRNPs. 3 . The ends of adjacent exons bond covalently, releasing the intron (which is then degraded). A A
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RNA Processing Events in Eukaryotes - addition of “cap” to 5’ end of RNA - addition of poly A “tail” to 3’ end of RNA - RNA splicing - removal of introns…. portions of the RNA not used in translation - conducted by spliceosome (RNA/protein complex) Human Dystrophin Gene X chromosome Largest known mammalian gene 2.7 million bp 78 introns mRNA is 14,000 bp
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RNA Processing Events in Eukaryotes - addition of “cap” to 5’ end of RNA - RNA splicing - removal of introns…. portions of the RNA not used in translation - conducted by spliceosome (RNA/protein complex) - addition of poly A “tail” to 3’ end of RNA - RNA export to cytosol
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DNA Replication RNA Protein Transcription Translation THE CENTRAL DOGMA
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Translation – Basic Features - synthesis of a polypeptide using information in RNAs - carried out by a ribosome - occurs in the cytosol How is a nucleic acid “language” converted into a protein “language”?
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Translation – Requires 3 Types of RNA mRNA (messenger) – specifies the sequence of amino acids in a protein rRNA (ribosomal RNA) – component of ribosomes tRNA (transfer RNA) – links nucleic acid information to amino acids
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