Transcript 10. Translation

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: ?