The nucleic acids (DNA and RNA) are informational molecules, set of directions by which they can duplicate themselves and guide the synthesis of proteins. The synthesis of proteins-most of which are enzymes-ultimately governs the metabolic activities of the cell (Lodish et al., 2004). The stress induced biochemical changes are described as secondary responses of the fish. The biochemical analysis of DNA, RNA and proteins are considered as markers in the toxicity study. Inhibition of DNA synthesis, thus might affect both protein as well as amino acid levels by decreasing the level of RNA in protein synthesis machinery. Pesticides are potential inhibitor of DNA synthesis, which might result in reduction of RNA level. The first half or one half of homogenate was mixed with diphenylamine reagent and kept aside for 20 hrs. After 20 hrs the colour developed was read at 595 nm. The standard graph was plotted with standard DNA (Calf thymus) supplied by the Sigma chemical company, with the aforesaid method. The other part of homogenate was mixed with Dischi-orcinol and heated at 900C for 15 minutes. After cooling at room temp., the colour developed was read at 655 nm. The standard graph was plotted with standard RNA (Baker’s yeast) supplied by Sigma chemicals company. The results in 4 and 8 days sublethal exposure of phosalone Table V.3 and Figure V.3 indicates heterogeneous levels of DNA in the tissue of liver, brain, muscle, gill and kidney. Under lethal and sublethal exposure to Phosalone for 24hr, the percentage of depletion was found in all the tissues of test fish, maximum percentage of depletion was in Gill (+26.17) and (-29.68), minimum depletion in liver(+1.42) and (-21.99) in brain. Under sublethal exposure to Phosalone for 4th and 8th days, the glycogen levels was found to decreased all the tissues of test fish Ctenopharyngodon idella and maximum depletion was in muscle (-43.20) and (-86.03), minimum decrease was observed in kidney (-0.47) and(- 40.23) in gill.