dna extraction from peas

Hypothesis

It is to be expected that it will be possible to extract DNA from a pea.

Safety Assessment

Method

1. 50g of garden peas were mashed with a pestle and mortar, adding a little of the extraction buffer (washing up liquid) to help with the mashing process.
2. Then the mashed peas were carefully transferred into the beaker containing the rest of the extraction buffer.
3. The beaker was then placed into a water bath at a temperature of 60°C for exactly 15 minutes.
4. The mixture in the beaker was then left standing on ice for two minutes and then mashed carefully with a pestle and mortar in small batches.
5. The mixture was then placed through coarse filter paper – to remove all of the cell debris.  
6. 10ml of the filtrate was then poured into a test tube and 3 drops of protease was added.  The test tube was then placed into ice to keep cold.
7. Then, using a pipette, 10ml of ice-cold ethanol was added down the side of the test tube – resulting in two distinct layers of liquid.
8. The air bubbles will then carry the DNA to the ethanol layer, which can then be extracted.

Results

Interpretation

The results from this experiment show that the hypothesis stated at the beginning of the experiment is correct.  By using a pestle and mortar to break up the peas into a puree, as opposed to using a blender, the DNA is broken slightly – as apposed to it being shredded.  By using a detergent to help with the breaking down of the pea cell membrane – an intricate structure surrounding the membrane of phospholipids and proteins – causing them to precipitate (separate).  The heating at 60°C causes the DNA to breakdown – which is later slowed down, when cooking to prevent t he peas DNA from becoming denatured.  When filtering the mixture, the filtrate now contains the DNA along with soluble proteins.  By adding the ethanol down the side of the test tube, in a slow drip form, it prevents the DNA from breaking up and results in a shorter time for the strands to form.  The DNA of the pea is insoluble in freezing cold ethanol and will therefore precipitate into the upper ethanol layer via air bubbles.

 

Evaluation

If the experiment was to be repeated again, I would use a larger volume of peas, by doing so – it would result in a larger volume of DNA being extracted.  Further investigations of DNA extraction could be carried out by using blood or any other food product, providing that health and safety issues are dealt with.  If the DNA was to be extracted from the test tube, it could then be stained and examined further by using a technique called X-ray crystallography, as even the most powerful microscope is unable to detect any DNA image. (www. learn.genetics.utah.edu)

Reference

 (viewed 25/02/209)

 (viewed 25/02/209)

 (viewed 25/02/209)

 (viewed 25/02/2009)

Boyle, M., Senior, K., (Ed) (2002) Human biology. London: Harper Collins Publishers

Class notes and worksheets