genetic fingerprinting

• DNA of individuals except identical twins are unique
• 95% of DNA does not code for any characteristics
• number of times STR is repeated is what produces variations between individuals
• the more closely related 2 individuals are the more similar the sequence
• step 1 on genetic fingerprinting

  DNA is extracted from the sample
• step 2 on genetic fingerprinting

  fragments separated using gel electrophoresis

  fragments injected into wells and electric current is run through

  DNA is attracted to the positive gel
• step 3 on genetic fingerprinting

  gel immersed in alkali in order to separate strands

  fragments transferred to the nylon membrane
• step 4 on genetic fingerprinting

  Radioactive probes are used to attach to the core sequences

  probes have complementary bases to STRs

  probes not bound are washed off

  membrane is dried
• step 5 on genetic fingerprinting

  nylon sheet is placed under x-ray film

  radioactive probes on DNA expose film

  produces light or dark bands

  fragments are analysed
• Southern blotting

  thin nylon membrane is laid over gel

  membrane covered with several sheets of paper which draws up liquid containing DNA by capillary action

  this transfers DNA fragments to nylon membrane

  DNA fragments fixed on by UV light
• medical problems

  can be used to determine parents of child

  information can be used for:

  paternity suits

  inheritance cases

  immigration cases
• crime problems

  DNA pattern compared with victim

  if there is a match can be used as evidence
• is genetic fingerprinting reliable (agree)

  everyone's DNA is unique
• Is genetic fingerprinting reliable (disagree)

  there could be contamination

  identical twins have same DNA
• the higher the number of bands in common the closer the relationship