Genes and the triplet code

• Genes are a section of DNA located at a particular locus
• The base sequence of each gene carries the genetic code for the amino acid sequence it codes for and functional RNA
• Introns are sections of genes containing non-coding DNA
• Exons are sections of genes containing coding DNA
• Introns occur both within and between genes
• Prokaryotic DNA doesn't contain any introns
• Properties of genetic code

  • degenerate = most amino acids coded for have more than one triplet
  • universal = same triplets of DNA bases code for the same amino acids in all organisms
  • non-overlapping = each base in each triplet is read only once
• Genetic code is read in triplets
• DNA contains 4 different nitrogenous bases