LOCATING GENES

• WHAT ARE DNA PROBES?

  short, single-stranded lengths of DNA with bases complementary to a target sequence/gene, with a fluorescent marker gene/ tag attached
• TYPES OF LABELS THAT ARE USED IN DNA PROBES?

  RADIOACTIVE

  • nucleotides with 32P isotope
  • detected using X-ray film

  FLUORESCENT

  • emit light when probe binds to DNA sequence
  • detected using microscope
• PROCESS OF DNA HYBRIDISATION?

  1. Determine base sequence of mutant allele
  2. DNA fragment with base sequence complementary to allele produced
  3. Copy using PCR
  4. Attach marker to form probe
  5. Person's DNA heated to separate strands
  6. Strands cooled in mixture containing probes
  7. If allele of interest present, probe will bind by complementary base pairing
  8. Wash off excess, unattached probes
  9. Hybridised DNA is labelled and can be detected
• USES OF DNA HYBRIDISATION?

  • genetic screening (requires genetic counselling)
  • personalised medicine (genotype, efficacy, dosage)
• WHAT IS GENETIC SCREENING USED FOR?

  • inherited diseases
  • responses to drugs
  • health risks
• EVALUATION OF GENETIC SCREENING?

  -if increased risk of disease, people can be refused life or health insurance and jobs

  -causes stress and anxiety when patients are informed
• PERSONALISED MEDICINE?

  tailored to your genotype

  + more effective

  + fewer side effects

  -expensive

  -not available to all

  -two-tier health system