Summary:- In general, Deoxyribonucleic acid (DNA) contains the genetic information, used in the development and functioning of living organisms. It is often called as a blueprint, since it contains the genetic information, from which the components of celObesity represents a disruption in balancing fuel intake with energy expenditure in favor of energy conservation. Adiposity is known to be carefully regulated and, over time, highly resistant to major changes, raising questions about how energy homeostasiThis work aim to study:Effect of obesity on gene expression of tissue DNAEffect of obesity on anti oxidants. For this our search aimed to study the effect of obesity through feeding high caloric diet with high fat content on tissue genes expression in liver and muscle and compare it with the same genes in low caloric diet try Fifty male Albino rats were used in the study. Their weight ranged from 120 gm .Rats will be housed in stainless steel cages in the laboratory house in biochemistry department which will adapted to the room and cage environment 7 day before the beginning The result of the study can be summarized as follows:1- Effect of obesity and conjugated linoleic acid (CLA) treatment on Body weight:There is highly significant increase in the body weight of obese group in comparison with its control one that considered indication of obesity occurrence, but significantly decrease in conjugated linoleic acid(CLA) treatment which treated with conjugated2- Effect of obesity and conjugated linoleic acid (CLA) treatment on lipid profile:We measured lipid profile for obesity indication. there is very high significant increased in the concentration of total lipid ,total cholesterol, triglycerides ,LDL and VLDL in obese group in comparison with its control ,but significantly decreased of HD3- Effect of obesity and conjugated linoleic acid (CLA) treatment on catalase (CAT) activity in kidney homogenate:There is significant decrease in the activity of catalase in obese group than control one but increase in Conjugated linoleic acid (CLA) treatment than control.4- Effect of obesity and conjugated linoleic acid (CLA) treatment on catalase(CAT) activity in muscle:There is significant decrease in the activity of catalase in obese group than control one but increase in Conjugated linoleic acid (CLA) treatment than control.5- Effect of obesity and conjugated linoleic acid (CLA) treatment on catalase(CAT) activity in liver homogenate:There is significant decrease in the activity of catalase in obese group than control one but increase in Conjugated linoleic acid (CLA) treatment than control.6- Effect of obesity and conjugated linoleic acid (CLA) treatment on superoxide dismutase (SOD) activity in muscle homogenate :There is a significant decrease in the activity of superoxide dismutase in obese group than control one but increase in Conjugated linoleic acid (CLA) treatment than control.7- Effect of obesity and conjugated linoleic acid (CLA) treatment on superoxide dismutase (SOD)activity in kidney homogenate:There is a significant decrease in the activity of superoxide dismutase in obese group than control one but increase in Conjugated linoleic acid (CLA) treatment than control.8- Effect of obesity and conjugated linoleic acid (CLA) treatment on superoxide dismutase (SOD)activity in liver homogenate:There is a significant decrease in the activity of superoxide dismutase in obese group than control one but increase in Conjugated linoleic acid (CLA) treatment than control.9- cytochrome oxidase subunit I mRNAExpression in liver:There was significantly up regulation in pattern of expression.10- cytochrome oxidase subunit I mRNAExpression in muscle:There was significantly down regulation in pattern of expression.11- ATPase mRNAExpression in liver:There was significantly up regulation in pattern of expression.12- ATPase mRNAExpression in muscle:There was significantly down regulation in pattern of expression.13- B- actin mRNAExpression in liver and muscle:There were stabilized pattern of expression in all groups as it considered as hosekeeping gene which act as internal control.Conclusion1- Obesity is correlated with an increased risk of death , and is a risk factor for a number of chronic conditions , including adult onset diabetes, hypercholesterolemia and high plasma triacylglycerols,2- There is significant decrease in the activity of superoxide dismutase in liver , muscle and kidney homogenate of obese group than control one but increase in Conjugated linoleic acid (CLA) treatment than control to overcome oxidative stress..3- There is significant decrease in the activity of catalase in liver , muscle and kidney homogenate of obese group than control one but increase in Conjugated linoleic acid (CLA) treatment than control to overcome oxidative stress.4- The rate of mutation in mtDNA is calculated to be about ten times greater than that of nuclear DNA, possibly due to a paucity of DNA repair mechanisms. This high mutation rate leads to a high variation between mitochondria, not only among different spe5-A certain mutation can cause several different diseases depending on the severity of the problem in the mitochondria and the tissue the affected mitochondria are in. Conversely, several different mutations may present themselves as the same disease.6- There is significant increase in gene expression of cytochrome oxidase and ATP synthase in obese rats in liver. Due to Production of ROS increased selectively in adipose tissue of obese rat, accompanied by augmented expression of cytochrome oxidase and