genetic code features

• Genetic code


  • Degenerate
  • Universal
  • Non-overlapping
• Start codon


  The first three bases on DNA/mRNA that initiate translation
• Stop codon


  The final three bases on DNA/mRNA that cause the ribosome to detach and translation to stop
• Start codon codes for the amino acid methionine, which later gets removed
• You don't need to know the specific start/stop codon sequences or the amino acids they code for
• Degenerate


  Each amino acid is coded for by more than one triplet of bases
• There are 64 possible triplet combinations (4^3) but only 20 amino acids
• Degenerate code means a mutation in one base may not change the amino acid coded for
• Universal


  The same triplet of bases codes for the same amino acid in almost all living things
• Universal code allows genetic engineering between species
• Non-overlapping


  Each base is only part of one triplet, they are read as discrete units
• Non-overlapping means a mutation only affects one amino acid
• Introns


  Sections of DNA that don't code for amino acids, found in eukaryotes
• Exons


  Sequences of DNA that do code for amino acids
• Genome


  An organism's complete set of DNA within one cell
• Proteome


  The full range of proteins in one cell
• Genome size varies greatly between organisms, e.g. humans have 3 billion base pairs, bacteria have 600,000