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Extracting DNA
WALT: To carry out a practical to extract DNA from
onion cells.

WILF:
~ Recall where DNA is found inside p...
Method
1. Finely chop an onion, crush in the mortar with the
pestle and add them to a large beaker.
2. Add 8 teaspoons of ...
What’s happening?
DNA is found in the nucleus of
the cell. To extract this we need
to break through the cell wall
and cell...
Method
1. Take a boiling tube and fill a third of the way with
some of filtrate. Take another boiling tube and fill a
quar...
Hopefully what you should of
saw is…
Strands of DNA
B2.4 extracting dna
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B2.4 extracting dna

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B2.4 extracting dna

  1. 1. Extracting DNA WALT: To carry out a practical to extract DNA from onion cells. WILF: ~ Recall where DNA is found inside plant and animal cells. (D) ~ List the steps taken during the practical which helps to extract the DNA. (C) ~ Describe some implications that the HGP has had in the world of science and medicine. (B) ~ Evaluate the impact of the HGP. (A/A*)
  2. 2. Method 1. Finely chop an onion, crush in the mortar with the pestle and add them to a large beaker. 2. Add 8 teaspoons of salt, 70cm3 of washing up liquid and 200cm3 of warm water to the beaker. 3. Leave for 5mins but stir intermittently. 4.Place some filter paper into a funnel and place over a conical flask. 5. Gently pour some of the mixture into the funnel and let it drain through. 6.Ensure you write you and your partners name onto the conical flask ready for next lesson.
  3. 3. What’s happening? DNA is found in the nucleus of the cell. To extract this we need to break through the cell wall and cell membrane. It attracts fats therefore causing the cell membrane to collapse. The salt binds to the DNA allowing us to see it.
  4. 4. Method 1. Take a boiling tube and fill a third of the way with some of filtrate. Take another boiling tube and fill a quarter of the way up with ethanol. 2. Tilt the boiling tube and very slowly pour the ethanol down one side. This should take a few minutes and the surgical spirit will form a layer. 3. Place your boiling tube in a rack and leave to settle for about 10mins. (See board for ‘To do’ list!) 4. You should now see a white layer forming between the filtrate and ethanol, this is DNA. 5. Use a pair of forceps to extract some of the DNA.
  5. 5. Hopefully what you should of saw is… Strands of DNA

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