Molecular structure of DNA:
DNA molecule is made up of three units. These are nitrogenous bases:
1. Sugar and
2. Phosphoric acid
Nitrogenous bases:
DNA molecule contains two types of nitrogenous bases i.e., purine bases and pyrimidine bases.
1. Sugar:
2. Deoxyribose sugar (pentose sugar) is present in the DNA molecule. It contains a five-membered heterocyclic ring and is generally called pentose sugar.
Arrangement of constituents in DNA molecule:
A combination of base and Sugar is known as a nucleoside. Similarly, base, sugar phosphates form nucleotides. DNA molecules are the polymer of nucleotides.
Nitrogenous base + Sugar = Nucleoside
Nucleoside + Phosphoric acid = Nucleotide
Nucleotides = Polynucleotide
DNA is a macromolecule consisting of two polydeoxyribonucleotide chains. Each polydeoxyribonucleotide is formed by linkage of many deoxyribonucleotides through phosphodiester bonds. These bonds are present between two adjacent nucleotide components.
In DNA molecules Adenine base joined with Thymine base by a double bond and cytosine with guanine by triple bond ie., A = T, C = G.
