DNA profiling

• what is the genome of an organism?

  • all of the genetic material it contains
  • DNA in the mt and nucleus combined
• what are chromosomes made up of?

  made up of millions of base pairs
• what are exons?

  regions of DNA that code for proteins
• what are introns?

  regions of DNA that don't code for proteins
• what is a gene?

  a region of DNA that codes for a protein
• what did sir Alec Jeffreys do in the field of DNA profiling?

  • located tandem repeat sequences of DNA (repetitive fragments that don't code for proteins)
  • Created the technique of DNA profiling
• what are the five key stages of DNA profiling

  1. extracting DNA
  2. digestion of sample
  3. separating DNA fragments
  4. hybridisation
  5. seeing evidence

  Edith's DNA seems highly sickening
• what is DNA profiling?

  • helps assist in the identification of individuals or familial relationships
• state what's involved in extracting DNA?

  • extract from human tissue
  • can use PCR to obtain the smallest fragment possible which will be enough DNA to help scientists develop a profile
• state what's involved in digesting the DNA sample

  • DNA cut into smaller fragments using restriction (enzyme) restriction endonuclease
  • cut DNA at a specific nucleotide sequence, known as restriction site. makes 2 cuts- one through each DNA strand
  • allow scientists to cut DNA at specific points in the introns
• what happens during the separation of DNA fragments?

  • fragments of DNA are separated to from a clear pattern
  • use technique called electrophoresis
  • electrophoresis utilises the way charged particles move through a gel medium, smallest fragments travel furthest
  • DNA then immersed into alkali to separate DNA from double strands into single strands
  • strands then transferred onto membrane by Southern blotting
• what happens during hybridisation?

  • DNA probes (short DNA or RNA sequences complementary to a known DNA sequence) added in excess to the DNA fragments to label fragments (using radioactive/fluorescent dye)
  • hybridisation- probes bind to complementary strands of DNA under right pH and temp
  • identify microsatellite regions
  • excess probes are then washed off
• state what happens in the process of seeing the evidence

  • if radioactive labels added to DNA probes, X ray images taken of the membrane
  • if dyes- membrane placed under UV light so the tags glow
  • fragment gives a pattern of bars (DNA profile) which is unique to every individual apart from identical twins
• why are introns useful in DNA profiling?

  • unique in every individual
  • Doesn't affect survival
• why is DNA profiling useful?

  • can be used in forensics
  • can be used to analyse the risks of disease