lecture09 - Lecture 9: Wednesday, May 26, 2010 Biology 172...

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Unformatted text preview: 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 RNA Processing- prokaryotes use RNA immediately in translation- eukaryotes “process” RNA before it is used 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 ′ 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 ′ 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 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 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 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 DNA Replication RNA Protein Transcription Translation THE CENTRAL DOGMA 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”? 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 The triplet code is non-overlapping and continuous...
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This note was uploaded on 09/13/2010 for the course 172 bio taught by Professor Raji during the Spring '10 term at University of Michigan.

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lecture09 - Lecture 9: Wednesday, May 26, 2010 Biology 172...

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