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2ALecture 14 - Translation DNA RNA Protein Lecture 14 More...

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2/9/10 1 Lecture 14 More on translation Translation DNA RNA Protein 1. Overview of Translation 2. The Translation Machinery 3. The Mechanics of Translation A-T-G-T T-G-C-A A-U-G-U 5’ 3’ RNA DNA AA1-AA2-- PROTEIN Gene to protein Gene Protein 5' 3' NH 3 + COO - Transcription Translation AU GA C UU U U U A A A A AA C C C C G DNA polymerase moves from the 3’ to the 5’ end of its template strand. RNA polymerase moves fro the 3’ to the 5’ end of its template strand. How does the ribosome move? From the 3’ to the 5’ end of the mRNA From the 5’ to the 3’ end of the mRNA mRNA termination elongation Overview of translation initiation aminoacyl tRNAs* ribosome *tRNA part not shown Translation machinery • tRNAs carriers of amino acids amino acid here to make “aminoacyl tRNA” tRNA structure cartoon of a tRNA 3’OH Guides amino acid to the right codon anticodon
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2/9/10 2 Aminoacyl tRNA Synthetases Enzymes that join amino acids to tRNAs. Each recognizes an R group and an anticodon. OH O C C NH 3 + H CH 3 OH U C G H 2 O 2Pi Δ G ~ 0 Δ G Δ G a. a. activation charging of tRNA ATP O O C C NH 3 + H CH 3 P~P ~AMP O U C G O C C NH 3 + H CH 3 AMP 1 synthetase --> 2 reactions What’s “aminoacyl” ? O O C C NH 3 + H CH 3 ~AMP Aminoacyl-AMP O U C G O C C NH 3 + H CH 3 Aminoacyl-tRNA tRNA synthetases are a critical step in the genetic code! There are 20 synthetases–one for each aa But there are 61 codons. How many different tRNAs might each synthetase have to recognize? a. Just 20, for 20 amino acids b. 61, because each codon needs the right anMcodon c. Somewhere between 20 and 61, because of “wobble base pairs” tRNAs carry weird, modified nucleotides that promote wobble base-pairing No, please don’t memorize the details in this table Most tRNA synthetases have to recognize several different tRNAs Which synthetases clearly only have to recognize 1 tRNA?
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