Isolation of Plant Genomic DNA Cheat Sheet

Isolation of plant (Onion) genomic DNA by a crude method.

A general difficulty in isolating DNA from plant cells is the presence of a cell wall, which requires degrad­ation either physically or enzyma­tic­ally. Specific plant species and tissues may have additional challenges due to starches or phenolic compounds.

Extract genomic DNA from onion.

All DNA isolation methods consist of three steps:
Lysis of cells.
Denatu­ration of histones associated with DNA.
Precip­itation of DNA using an organic solvent like ethanol.

In the described method:
1. A kitchen blender (mixer Grinder) breaks open the cell walls.
2. Detergent degrades the phosph­olipid membranes around the nuclei, releasing the DNA.
3. Detergent, combined with heating, denatures the histones associated with the DNA.
4. Protease hydrolyses the denatured histones into peptides and amino acids.
5. DNA is then precip­itated in ice-cold ethanol, which disrupts DNA-water intera­ctions, causing DNA to precip­itate out of solution.

MATERIALS
Onion
Washing-up liquid (Deter­gent)
Table salt (3 g)
Water (tap water is suitable)
Very cold ethanol or Isopro­panol (10 ml) (keep in the freezer)
a protease enzyme, (2–3 drops) (Optional)
Ice
Cheese­cloth
EQUIPMENT
Plastic funnel
Beakers, 2 (250 ml)
Test tubes, 2
Plastic spoon for stirring the mixture
Chopping board
Knife for chopping onion
Water bath, maintained at 60°C
Mixer Grinder or liquidiser