A total of 27 burger

products were

analysed, with 10 of

them containing

traces of horse DNA

and 23 containing pig

DNA.

Extracting DNAWALT: 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*)

Method1.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.

What’s happening?

It attracts fats therefore causing the cell membrane to collapse.

DNA is found in the nucleus of the cell. To extract this we need to break through the cell wall and cell membrane.

The salt binds to the DNA allowing us to see it.

Method1. 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 saw is…

Strands of DNA