Monday, 9 July 2012

Extracting Onion DNA

Last year we did a first investigation into genetics and heredity, by demonstrating how play dough monsters offspring would look.
We moved on to look at cell structure and then DNA extraction from an onion.

First finely chop an onion.

Before we began the DNA extraction, 
we had a look at the onion cells under the microscope.

Then we coated the onion in washing-up liquid and added half a teaspoon of salt. This helps to break down the onion's cells.

Add two tablespoons of water and stir.
Leave for ten minutes.
Stir again.
Strain the liquid into a glass bowl.

Pour surgical spirit down the inside of the jar.
Leave for 20 minutes.

After 20 minutes, a stringy white substance will appear in the top layer. 
This is the onion's DNA.

We did a family quiz, to investigate 
which traits are controlled by nature and which are left to nurture.
We finished off by compiling a family tree, back to grandparents.


  1. Wow - what a great experiment! I would never have thought to do something like this, I bet you guys learnt a lot!

  2. I like that you looked at the cells under the microscope first. I have not heard of using surgical spirit before. (In fact, I have never heard of surgical spirit before.)



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