each of which is composed of a nitrogen base, a pentose sugar and a phosphate. A purine or a pyrimidine and a ribose or deoxyribose sugar is called nucleoside . A nitrogenous base is linked to pentose sugar through n-glycosidic linkage and forms a nucleoside. When a phosphate group is attached to a nucleoside it is called a Figure .
: Structure of nucleic acid component Telomerase - A ribonucleic Protein. T e l o m e r e protects the end of the chromosomes from damage. Telomerase is a ribonucleo protein also called as terminal transferase. - - .
. PM . . Formation of Dinucleotide and Polynucleotide Two nucleotides join to form dinucleotide that are linked through ′ - ′ phosphodiester linkage by condensation between phosphate groups of one with sugar of other.
This is repeated many times to make polynucleotide . Nucleoside Nucleotide It is a combination of base and sugar. It is a combination of nucleoside and phosphoric acid. Examples Examples Adenosine = Adenine + Ribose Adenylic acid = Adenosine + Phosphoric acid Guanosine = Guanine + Ribose Guanylic acid = Guanosine + Phosphoric acid Cytidine = Cytosine + Ribose Cytidylic acid = Cytidine + Phosphoric acid Deoxythymidine = Thymine + Deoxyribose Uridylic acid = Uridine + Phosphoric acid Friedrich Miescher was the first to isolate a non-protein substance in nuclei of pus cells and named it as ‘ Nuclein’ .
Figure . : Basic component of DNA and RNA . . Structure of DNA Watson and Crick shared the Nobel Prize in for their discovery, along with Maurice Wilkins , who had produced the crystallographic data supporting the model.
Rosalind Franklin ( – ) had earlier produced the first clear crystallographic evidence for a helical structure. James Watson and Francis Crick of Cavendish laboratory in Cambridge built a scale model of double helical structure of DNA which is the most prevalent form of DNA, the B-DNA . This is the secondary structure of DNA. Figure .
: Watson and Crick As proposed by James Watson and Francis Crick , DNA consists of right handed double helix with helical