mutations

• Mutation

  A change in the DNA base sequence
• Mutations happen spontaneously in our cells all the time, particularly when DNA is being duplicated before cell division like in mitosis
• Things that increase the risk of mutations

  • Carcinogens (harmful chemicals like in cigarette smoke)
  • Certain types of radiation (like x-rays or gamma rays)
• These things don't always cause mutations, they just increase the risk of a mutation occurring
• Gene

  A section of DNA that codes for protein
• Triplet/Codon

  A group of 3 bases that codes for one of the 20 different amino acids
• How DNA works to create proteins

  1. Triplets/codons code for amino acids

  2. Amino acids combine in the correct order to form a protein chain

  3. Protein chain folds to form a protein
• A mutation that changes a single base can change the amino acid that the codon codes for, which can have knock-on effects on the protein's shape and function
• Most mutations don't have a significant effect, either because they only affect the protein slightly or because they occur in non-coding DNA that doesn't code for proteins
• Non-coding DNA


  DNA that isn't part of any gene and doesn't code for protein, but can play a role in gene expression
• Types of mutations

  • Substitutions (one base changed)
  • Insertions (extra base inserted)
  • Deletions (base deleted)
• Insertion and deletion mutations are worse than substitutions because they shift all the subsequent codons, completely changing the amino acid sequence