WALT: To carry out a practical to extract DNA from
~ Recall where DNA is found inside plant and animal cells.
~ 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*)
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
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.
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
the cell membrane
The salt binds
to the DNA
allowing us to
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.
Hopefully what you should of
Strands of DNA