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10. Translation Chapter 27 Lehninger 5th Edition Translation • mRNA gets translated by Ribosomes Bacterial ribosomes Eukaryotic ribosomes in ER The Genetic Code • 4 bases -> 20 amino acids? • 42 = 16 43 = 64 • Code = – Triplet code • 3 bases -> 1 amino acid – Non-overlapping – Degenerate The Genetic Code Codons Codon usage Ribosomes • Need to: – Bind to mRNA – Recognise start of coding sequence – Move along coding sequence • Read RNA, codon by codon • Add amino acids to protein chain • Need an “adaptor” molecule – tRNA – Transfer RNA tRNA: Transfer RNA 20 tRNA synthetases 1965: Yeast tRNAala Ribosomes: 2 subunits • large • small • S: Svedberg units; centrifugation “size” Chuck Kurland SSU rRNA Translation Initiation •Bacteria: RBS or Shine Dalgarno sequence •Eukaryotes: ?