General introduction of genetic material

Deoxyribonucleic acid (DNA) and  ribonucleic acid (RNA) are the two types of nucleic acids found in living systems. DNA acts as the genetic material in most of the organisms. RNA though it also acts as a genetic material
in some viruses, mostly functions as a messenger. DNA is found as long thread like forms or circular forms RNA is of many types : double stranded  RNA is found only in viruses and act as genetic RNA , non-genetic RNA is also of many types : m RNA , hRNA , t RNA , r RNA etc.

Structure of Polynucleotide Chain
 A nucleotide has three components – a nitrogenous base, a pentose sugar (ribose in case of RNA, and deoxyribose for DNA), and a phosphate group. There are two types of nitrogenous bases – Purines (Adenine and Guanine), and Pyrimidines (Cytosine, Uracil and Thymine).Thymine is present in DNA. Uracil is present in RNA at the place of Thymine.

- Deoxiribose suger + base together are joined by N-glycosidic bond and forms a nucleoside.

1) AT 5’end of sugar in nucleoside, phosphate is joined to carbon by phosphodiester bond and forms a nucleotide So at 5’end free phosphate group is present.

2) AT 3’end of nucleotide free oh- group is present.

3) Adenine pairs with thymine by 2 hydrogen bonds in DNA and with urecil in RNA. Cytosine pairs with guanine by 3 hydrogen bonds.