Mutations

• Gene knockout


  • Uses CRISPR cas 9
  • Used to investigate the function of a gene
• Knockout libraries


  • Exist for animals
  • Observe phenotype changes
• CRISPR Cas 9


  • Bacterial endonuclease causing a double strand break
  • Allows scientists to modify specific section of DNA
• CRISPR Cas 9


  1. Guide RNA is used to target a specific DNA sequence

  2. A PAM sequence helps cas 9 bind to DNA

  3. Cas 9 cuts the gene at the specific sequence

  4. They can knockout the gene or insert DNA where cut
• Bacteria/prokaryotes


  • Use CRISPR cas 9 to defend against viruses
  • Incorporate short sequences of foreign DNA into their own genome as spares
  • Creates a record of previous infections
  • Allows bacteria to find and destroy similar foreign DNA
• Uses of CRISPR Cas 9

  • Gene therapy -> sickle cell anemia
  • Genetic research - understand actions of genes
  • Malaria prevention - modify mosquito genomes
  • Agriculture - crops with desirable traits
  • Genetic energy of microorganisms - modify bacteria/yeast
• Ethical concerns with CRISPR Cas 9

  • Unintended mutations
  • Cost
  • Misuse
  • Unpredictable in embryos
  • Decrease diversity
  • Issues with standard regulations
• Types of mutations


  • Substitution
  • Insertion
  • Deletion
• Sickle cell anemia


  Example of a substitution mutation
• Huntington


  Example of an insertion mutation
• Deletion of CCRS


  Makes one immune to HIV
• Frameshift mutations


  • Caused by deletions or insertions
  • Chain reaction
• Types of mutation effects

  • Silent
  • Missense
  • Nonsense
• Missense mutation


  Different amino acid
• Nonsense mutation


  Codes for a stop codon
• Mutagens


  • Radiation
  • Chemicals (carcinogens, tobacco smoke)
  • Infection agents (HPV)
• Germ line mutation


  • Ovary/testes
  • Germ line cells make gametes
  • Mutations can be passed onto the offspring
• Somatic mutation


  • Mutation of body cells
  • Localized
  • Not passed onto offspring
• Conserved sequence


  Identical or similar sequences of nucleic acids across a species
• Highly conserved sequence


  Identical or similar genes/nucleic acids over long periods of evolution
• Hypotheses for highly conserved sequences

  • Functional constraint - essential for cell function and reproduction, mutations are naturally selected against
  • Slower rates of mutation - under selective pressure to maintain their function, slower rate of mutation