Question

What kind of a macromolecule is DNA? What is the chemical reaction involved in the precipitation of DNA? Why is it important to extract DNA?

Answer 1

DNA as a macromolecule: DNA stands for Deoxyribo nucleic acid. It is a nucleic acid made up of monomeric unit called Nucleotide. A nucleotide consist of -

a) Sugar - Deoxyribose in DNA ( ribose in RNA)

b) An organic base- Adenine, cytosine, guanine and thymine(in DNA)( In RNA its uracil instead of thymine).

c) And a Phosphate group.

Chemical reaction involved is Ethanol precipitation By using cold ethanol or Isopropanol (IPA) . Since DNA is insoluble in alcohols, it will clump together giving a pellet form upon centrifugation.

Precipitation is improved by adding sodium acetate. In presence of salt like monovalent cation Na+ ion, ethanol effectively precipitates DNA.

In solution the sodium acetate breaks up into Na⁺ ion and CH₃COO^-. The positively charged sodium ion neutralize the negative charge of phosphate group of DNA making the DNA less soluble in water.

DNA extractio is an important molecular biology procedure. It is important because , with this ability to extract DNA from an organism, scientists can observe, classify, sequence and use DNA for different purposes. They include-

1) By studying the DNA sequence of an organism or a human being , genetic disorders and diseases can be identified. Cure can be found out by identifying the cause and experimenting with this DNA.

2) Since DNA of every organism is unique, they can be sorted out in this level.

3) Altering the DNA would lead to genetically engineer some organisms to produce beneficial things.

4) DNA extraction is used in crime investigation and forensice medicine, many a times a suspect is convicted based on DNA samples alone when no other evidence is available.

5) It is important in Historical identification- identification of historical bodies, remains and genocide.