Not quite Silent Witness but we have extracted the DNA from an onion during our work on reproduction.
First get your equipment ready
and read the instructions
mix the onions with salt water
and grind together to crush the cells and dissolve the DNA
the more its ground the better
Then we need to filter the insoluble onion out of the mixture
We use cloth to filter the insoluble bits
The residue stays in the filter funnel
The filtrate passes through into the measuring cylinder
We have to collect 50ml
Then we add washing up liquid to the filtrate
this must be stirred in carefully as we don't want any froth
One class recorded their experiment photographically using the ipad
Careful mixing
Just one spoonful
Now we need cold ethanol
This must be poured in carefully
down the edge of the beaker
so that the ethanol floats on top of the solution
if you are careful enough
then you get two distinct layers
with a sort of white fluffy boundary
this white stuff is the DNA
which looks stringy
well there is about 1m length of it in each cell!
The DNA is the middle layer here
