Lecture 8 5:23 - Biology 172 Lecture 9 Monday Todays Outline RNA Processing cap tail splicing Translation Overview The Genetic Code tRNA

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Lecture 9: Monday, May 23, 2011 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 Half of Lectures 8 and entire lecture 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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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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Are introns DNA relics of once functioning genes ie. “junk” that has been preserved during evolution??? Alternative splicing of introns within a gene may introduce greater variability of protein sequences translated from a single gene. Exons can be spliced together in different ways ie. gene contains 10 exons, one version of mRNA transcribed from that gene might contain exons 1-9. Another might contain exons 1-8 and 10. Alternative splicing allows production of isoforms, or, different forms of a protein from the same gene. Introns might get transcribed into microRNA (miRNA) that helps regulate gene expression.
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Alternative Splicing
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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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Figure 15.5 There are 4 RNA bases (U, C, A, G), and they must specify 20 amino acids. How many
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This note was uploaded on 01/21/2012 for the course BIOLOGY 172 taught by Professor Rajeshwarijanakiraman during the Spring '11 term at University of Michigan.

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Lecture 8 5:23 - Biology 172 Lecture 9 Monday Todays Outline RNA Processing cap tail splicing Translation Overview The Genetic Code tRNA

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