translation - begins when mRNA binds to rRNA 

• tRNA w/ complementary 3-nucleotide sequence (anticodon)
• 45 different tRNA molecules (some tRNA recognize more than 1 codon)
• activating enzymes - pairs 3-nucleotide sequences w/ amino acids
  • aminoacyl-tRNA synthetase - 1 exists for each of 20 common proteins, attaches tRNA to amino acids
  • corresponds to an amino acid and 1-6 different anticodons
• nonsense codons - UAA, UAG, UGA
  • has no complementary anticodon
  • used as “stop signals
• methionine - AUG, “start” signal
• initiation - begins w/ initiation complex formation
  • initiation factors - proteins that position tRNAfMet(in prokaryotes) or methionine (in eukaryotes) at P site, where peptide bonds form
  • A (aminoacyl) site - where successive amino-acid-bearing tRNA will bind
  • E (exit) site - where empty tRNA exit ribosome
  • positioning of mRNA determines reading frame
  • leader sequence - marks beginning of each mRNA
  • prokaryotes include several genes on a single mRNA (polycistronic mRNA)
  • eukaryotes include 1 gene per mRNA (monocistronic mRNA)
• elongation - elongation factor proteins bind tRNA to mRNA at A site
  • ribosome catalyzes reaction that removes amino acid from tRNA and creates peptide bond w/ next amino acid
• translocation - ribosome moves amino acids out, through E site
• termination - nonsense codons recognized by release factors (proteins that release polypeptides from ribosome)