Similarities in appearance and in body structure are some of the most striking examples of the operation of genes. If you look at families walking in a mall, it is easy to see similarities among family members. Body size is very genetically determined. In addition, a weak heart or a propensity for cancer can also be inherited. Nonetheless, it is important to realize that the practice of healthy lifestyle habits can mediate the effect of genes. It is important to counsel individuals about the power of healthy living in preventing disease and injury.