The present study aims to evaluate the water quality of two locations in Rosetta Branch of River Nile and its histopathological and genetic adverse effects on Nile tilapia (Oreochromis niloticus). Water and fish samples were collected from up and downstream of El-Rahawy Drain discharge point (location I and II, respectively) during the summer and winter seasons. The water quality, liver histopathology and DNA alteration of fish was examined. ISSR-PCR technique wa...