Genes are the units of heredity i.e. they transfer characteristics from parents to offspring and determine the characteristics of the offspring. Example- Transfer of hair color from parents to the offspring. Let’s say that the mother has dominant genes for black hair, (BB gene constitution) and the father has recessive gene for blonde hair (bb gene constitution). When fertilization will occur the mother will transfer one B gene for black hair to the zygote and the father will transfer one b gene for blonde hair to the zygote. The resulting offspring will have Bb gene for hair where B is a dominant gene and b is a recessive gene. Since B is dominant it will be expressed and b will be suppressed, the child will have black hair.