Nucleic Acid

Nucleic acids are biological macromolecules, essential for life.

Nucleic acids are classified into two classes that are Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA).

They are polynucleotides as their building block is a nucleotide.

The nitrogenous base combines with the pentose sugar and form a nucleoside.

When, a nitrogenous base combines with the pentose sugar and a phosphate group, a nucleotide is formed.

A polynucleotide chain is formed by the interlinking of a large number of nucleotides.

James Watson and F.C.H. Crick in 1953 proposed the three dimensional double helical model of DNA.

DNA is mainly present in the nucleus of a cell. Long and spirally coiled unbranched threads of DNA remain concentrated in the chromosomes of the eukaryotic cells. DNA, along with histone proteins, forms a nucleoprotein known as chromatin. Chargaff made observations on the bases and the other contents of the DNA and gave Chargaff’s rule. On the basis of shape, there are two types of DNA namely: a linier DNA and a circular DNA. On the basis of orientation, there are five types of DNA namely: A DNA, B DNA, C DNA, D DNA and Z DNA. Pallindromic DNA are certain regions in the DNA in which the sequence of nucleotides is same when read from either direction. DNA contains sense and antisense strands. This extra or junk DNA that does not have any function is called non-coding DNA.

Denaturation is a process of heating the DNA at a high temperature or treating it with acid or alkali, which leads to the uncoiling of the DNA strands.

Renaturation is a process in which the denatured DNA strands are provided low temperature treatments, leading to the formation of a DNA duplex.

RNA is made up of ribonucleotides, which are single chains of long and unbranched polymeric molecules. In RNA, uracil replaces thymine of DNA. It is of three types, messenger RNA, ribosomal RNA and transfer RNA. Some RNAs such as ribozyme and ribonuclease also have enzymatic activity.

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