dna extraction

• the first step

  disolve 3g of salt in 100cm3 water in a large beaker add 10cm3 washing up liquid stir gently until it disolves
• the second step

  thoroughly mash 50g peas in an empty beaker and add the solution made in the first step
• the third step

  place beaker in a 60c water bath for 15 mins
• the fourth step

  filter mixture collect the filtrate in a small beaker
• the fifth step

  measure 10cm3 filtrate and pour into a boiling tube
• the sixth step

  add two drops of protease.
• the seventh step

  tilt the boiling tube slightly and pour in ice cold ethanol letting it run down the sides. stop when there is as much ethanol as filtrate.
• the eigth step

  leave the tube for a few minutes. a white layer will form between the filtrate and ethanol - the dna
• the ninth step

  collect with a stiring rod.
• what does the detergent do?

  breaks down the cell surface membrame and
• what does the detergent do?

  breaks down the cell surface membranes and the membranes around the nuclei
• what does the salt do?

  makes the dna more likely to clump up
• what does protease do?

  it is an enzyme that breaks down proteins
• what does the ethanol do?

  dna is insoluble in ethanol so it forms a precipitate
• what is a precipitate?


  The solid that settles out of a solution.
• some people used to use horse meat and say that it was beef. during testing, dna was extracted from cells in the foods. the dna was then analysed to work out the order of some of the bases. different organisms have different orders of bases in certain genes, so these tests can identify which organisms have been used to make a food.
• why food scientists analyse the dna from meat products?

  to identify the organism the meat came from.
• safety precautions