Strawberry DNA Isolation

To officially christen the blog I've decided I'd do a DNA isolation. As I don't have access to any of the reagents we use in the lab I decided to find an at-home procedure online. I found this youtube video (below) and followed their procedure.



Overall it worked really well. I made two modifications:

1. I used a fork to pull out the strawberries chunks before I poured the cell mixture into the coffee filter. This prevented the coffee filter from getting clogged and made it easer to hold the filter with one hand.

2. I put the rubbing alcohol in the freezer before adding it to the cell mixture.

So how does this procedure differ from DNA isolation in a lab? And what is actually happening?

The Lysis

Below I compare the chemicals used in at Home DNA isolations to a Lab DNA isolation and their purpose.

Purpose Home Lab
Dissolves Cell Membrane Soap Triton X-100

Binds to DNA Table Salt NaCl2

Polar Buffer Water Tris-Cl

Denatures Proteins SDS

Removes Mg2 (PCR prep) EDTA

In a laboratory the next step would be adding phenol:clorophorm which destroys enzymes that digest DNA (DNAase).

After adding the phenol:chloroform the DNA is then spun in a centrifuge. This like the coffee filter separates all the cell chunks and debris from the DNA. It essentially creates two layers the bottom contains all the cell junk and the top contains your DNA. The top layer is then put into another tube and alcohol usually ethanol is added to precipitate the DNA.

The Precipitation

The video didn't explain well what is happening here, so I will. DNA is a negatively charged polar molecule. In liquids NaCL2 separates into Na+ and Cl- via a process called ionization. The negative charge on the DNA attracts the Na+ when this happens the DNA clumps. Now ethanol is relatively non-polar meaning it doesn't carry a charge. When added to the solution it forces the DNA to the surface. The same principle causes the oil to separate from vinegar when making Italian dressing.

Try this at home with your kids.

Cheers!