Isolating good quality DNA is an essential requirement for carrying out any genetic studies on plants and animals. It is also important to maintain the quality and yield of the DNA and avoid any cross contaminations during DNA extraction. Read this article to find out the important differences between plant and animal DNA extraction.

What is Plant DNA Extraction?

In plant DNA extraction, fresh leaves (15-20 days age) are taken and the cell wall is ruptured by mechanical grinding either in mortar-pestle or liquid nitrogen. The main objective of DNA isolation is to yield excellent quality of DNA molecules in a quick, inexpensive and consistent method. The principle behind the plant extraction method is to break the cell wall, cell membrane and nuclear membrane to release intact DNA molecules and later remove other cellular components such as proteins, phenols, lipids and secondary metabolites. The most common methods of plant DNA extraction are CTAB method and sodium dodecyl sulphate based method (Edward’s method).

Let us look at the CTAB buffer in brief.

• The CTAB buffer is composed of CTAB (Cetyltrimethylammonium bromide), NaCl, EDTA (ethylenediaminetetraacetic acid), Tris, PVP (polyvinylpyrrolidone) and β-mercaptoethanol. It is mixed with plant leaves and grinded mechanically.
• CTAB is a cationic detergent that weakens the cell wall along with the mechanical pressure exerted on the plant leaves.
• NaCl helps to remove proteins that are bound to the DNA.
• Tris is (hydroxymethyl) aminomethane is a buffer with pH ranging from 7 to 9 that increases the permeability of the cell wall.
• EDTA is a divalent cation that reduces the activity of cellular DNase and RNase.
• Β-mercaptoethanol clears the tannins and polyphenols so as to obtain pure DNA extract.
• PVP also removes all the phenolic compounds from the DNA extract.

What is Animal DNA Extraction?

Animal DNA extraction is commonly done using animal blood but sometimes muscle tissues or skin swabs are also used. Since animals do not have a cell wall, mechanical grinding is not required in the extraction. The most common method of extraction is the phenol-chloroform method. It is a liquid-liquid extraction technique that uses the principle of immiscibility to separate the upper aqueous phase and a lower organic phase.

The sample is lysed and mixed with equal amounts of phenol and chloroform and centrifuged. Two immiscible layers are obtained: an upper aqueous layer consisting of phenol, chloroform, nucleic acids, salts and sugars; and a lower organic phase that consists of the hydrophobic lipids along with proteins at the interphase of the two layers.

Plant vs Animal DNA Extraction

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Also see:

• Gonadotropin Releasing Hormone
• Plasma Membrane Structure
• Cell Wall and Cell Membrane