Deoxyribose nucleic acid or DNA is a complex made up of nitrogenous base, phosphodiester bond and sugar. It is a double stranded model given by Watson and Crick. The adenine bonds with thymine via double hydrogen bond. And cytosine bonds with guanine via triple hydrogen bond.
Nitrogenous bases
It is of to type : purines and pyrimidines. Purines are double ring nitrogenous base. These include adenine and guanine. The pyrimidines are single ring nitrogenous base. These include cytosine, thymine and uracil.
Phosphodiester bond
It consists of a central Phosphorus atom surrounded by one double bonded oxygen, one single bonded oxygen ion and and two oxygen singly bonded with phosphorus and one free Bond each.
Sugar
It is a pentose sugar.
The ribose sugar is present in RNA and the deoxyribose sugar is present in DNA. The phosphodiester bond connect the third carbon of one sugar molecule to the fifth carbon of another sugar molecule present just below it. The nitrogenous base are connected to the sugar by the first carbon of the pentose sugar ring.
Properties of DNA
It is present in double helical shape. The strands are anti-parallel to each other that is if one stand is going up the other will come down. The bonding of the nitrogenous base is complementary that is adenine bonds with thymine via hydrogen bond and cytosine bonds with guanine with triple hydrogen bond. In RNA thymine is replaced by uracil that is adenine bonds with uracil via double hydrogen bond.
Chargaff rule
The ratio of the sum of purine to the sum of pyrimidines is equal to 1.
