Genetic code

• What is the genetic code?

  The sequence of bases in DNA or RNA, this consists of triplet bases
• What are triplet bases?

  Three consecutive nucleotide bases on a DNA or RNA molecule that code for a particular amino acid, this is known as a codon
• What are introns and exons?

  Introns are non-coding regions of DNA that are transcribed but not translated into proteins. Exons are coding regions of DNA that are transcribed and translated into proteins.
• What is useful about a degenerate genetic code?

  • It reduces the phenotypic effect of mutations
  • mutations are mistakes in the base sequence e.g base deletion, insertion or substitution
  • A change in the base sequence can alter the amino acid sequence and therefore can alter the polypeptide
  • Some mutations are harmful e.g mutation leading to the production of sticky mucus causing cystic fibrosis
• Features of the genetic code:

  • Non overlapping- meaning each triplet code is only read once and triplets don’t share bases
  • Degenerate- meaning more than one triplet codes for the same amino acids
  • Start and stop codons- which either start or stop protein synthesis