The DNA is a molecule with a molecular weight ranging from 10000 to 20000 units. It is found in all organisms except certain viruses which have only RNA. It is the polymer compose of several repeating units called nucleotides. Each nucleotide is made up of 3 sub units
- 5 carbon sugar, pentose sugar
- Phosphoric acid
- Organic or nitrogenous base
These bases are adenine (A), guanine (G), cytosine (C), thymine (I). For RNA the bases are similar to these of DNA except that thymine is replaced by uracil (U). these bases can be grouped into two categories, A and G are double ring aromatic compound called purines while C and I are single ring aromatic compound called ryrimidines.
Using the four organic bases together with phosphoric acid and deoxyribobosomes with sugar different, nucleotides can be form, the bases are attached to the 5carbon sugar at position 1 to form a nucleoside by a condensation reaction, another condensation reaction joins the nucleoside with the phosphoric acid at position 5 to form the nucleotide.
Fig:
DNA is a polynucleotide whose chemical back bone is made up of phosphoether linkage between the sugar and the phosphate or phosphoric acid molecule. The base sequence of DNA is the primary determination of hereditary properties, the chemical analysis of a number of DNA samples indicates that the base do not occur in a random manner or fashion. The sum of purines bases equal totyrimedine that is: A=I and C=G.
