exam questions

• describe stage 1 of the PCR(3)

  • DNA is heated up to around 95 degrees
  • H+ bonds between the DNA strands break
  • DNA molecule breaks apart into seperate strands
• state the role of DNA primers in PCR(1)

  • provides a double stranded section of DNA for enzymes to bind to
  • defines region to be amplified/shows TAQ polymerase where to bind
• explain how TAQ polymerase is suitable for its role in PCR(3)

  • it joins free DNA nucleotides to make new DNA strands
  • does not denature in extremely high temperatures- extracted from bacteria which live in very high temps
• state 3 applications of PCR(3)

  • amplifying DNA found at crime scene for DNA profiling
  • amplifying DNA samples for genetic testing
  • amplifying patients DNA to test for genetic conditions
• which electrode DNA moves towards and which components of DNA give it its negative charge

  • DNA negative charge so moves towards positively charges anode
  • phosphate groups give it its charge
• describe stages of PCR and why to use it(4)

  • denaturation- 95 degrees, breaking hydrogen bonds
  • annealing-50/60 degrees, primers can anneal to single stranded DNA
  • elongation-72 degrees, optimum temp for taq polymerase, free nucleotides, complementary base pairing with DNA strand

  amplifies a small amount of DNA for DNA profiling
• outline the method by which DNA profiling is undertaken(6)

  • isolate DNA which can be extracted from biological sample
  • amplify DNA via PCR
  • use restriction enzyme to cut DNA into fragments and place florescent tags
  • fragments seperated using gel electrophoresis eg DNA placed in agarose wells and current passed through them
  • DNA fragments form different bands which are unique to the individual
• explain why 2 different alleles produced different amplified DNA fragments(3)

  • base sequence of alleles is different
  • so restriction enzyme cuts at specific DNA base sequence
• decribe how DNA profiling could be taken out to show 2 snakes are different species(4)

  • DNA sample from blood of both snakes
  • PCR on both DNA to amplify DNA
  • gel electrophoresis on both
  • compare different positions of bands, different in patterns show difference in genetics
• devise procedure using gel electrophoresis, to compare amplified DNA of 2 humans(4)

  • DNA gathered, cut using restriction enzymes and dyed with florescent tags
  • placed in wells of agarose gel
  • current passed through Gel, negative DNA attracted to anode
  • compare positioning of DNA fragments
• describe how DNA sample can be prepared for analysis using gel electrophoresis(3)

  • DNA cut into fragments using restriction enzyme
  • DNA dyed with fluorescent tags
  • fragments of DNA loaded into agarose gel/in wells
  • electric current passed through the gel- negative DNA fragments move towards the positive cathode
• explain how results of DNA analysis would show if 2 individuals are of the same species(2)

  • compare the positioning of the band(different due to different mass of fragments)
  • if they are closely related will have more similarities