Gene is that active part of DNA which can express itself by forming proteins. All the traits found in any organism is because of the proteins produced by genes. Thus genes are very important in controlling the traits of an organism. The total appearance of an organism is controlled by its genes. A gene is the one which decides whether the organism will be tall or short, what is going to be its skin color or eye color, presence or absence of body hairs is also decided by the genes only.