الفهرس 
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Abstract
The present study was carried out in the laboratories of the Genetics of Hydrobiology, at the National Research Center (NRC), Egypt during the period -#102;-#114;-#111;-#109; 2007 to 2010. br The objectives of the present study are: br 1-To assess the suitability of Nile tilapia (Oreochromis niloticus) fish as bioindicators for environmental pollution. br 2-To determine heavy metal (Cadmium and Copper) accumulation in fish organs (gills, liver, kidney and muscles) br 3-To investigate the genotoxic effect of heavy metals using micronucleus test (MN) and comet assays in blood cells. br 4-To investigate the genotoxic effect of heavy metal by evaluation the percentages of DNA fragmentation. br 5-To conduct protein banding patterns of Nile Tilapia muscles after treatment by cadmium/copper salts to test their potential as an indicator to the genotoxicity effect. br The results of this study are as the following: br 1. Determination of LC50: br Two concentrations of cadmium chloride (19.5 mg Cd/L) and copper sulfate (20.7 mg Cu/L) that caused LC50; 1/8 and 1/10 (2.44and 1.92 mg Cd/L and 2.59 and 2.07 mg Cu/L) were used to treat each of the two fish groups for 24 hours, 7 days, 14 days, 21 days and 28 days and these four treats were compared with their respective controls. br 2. Determination of water physiochemical parameters (APHA, 1985): br No significant variations referred to the water physiochemical parameters were determined under different conditions for heavy metals treated and untreated water. br 3. Analysis of fish samples: br High differences were found between treated samples and their negative controls, while low differences were found between treated samples and their positive controls using liver, kidney, gills and muscles fish organs which indicated the genotoxicity of these treated samples. br 4. Micronucleus test (MN): br Gills of fish samples treated with high doses of cadmium and copper for a long treatment duration showed higher frequencies of micronuclei than those treated with low doses and short treatment duration. br 5. Comet assay: Single Cell Gel Electrophoresis (SCGE): br Fish samples treated with high doses for long durations were more sensitive than those treated with low doses for short durations to DNA damage caused by cadmium and copper treatments. br 6. DNA fragmentation: br Muscles samples showed lower DNA fragmentation percentages caused by heavy metals and treatment durations than liver, kidney and gills samples with respect to their positive and negative controls. br 7. SDS-PAGE protein analysis: br Protein banding patterns of the tested muscles samples indicated the occurrence of variations due to heavy metals treatments by appearance or disappearance of band(s) with respect to their negative controls, especially after 28 days -#102;-#114;-#111;-#109; the beginning of the treatment.