All living things inherit their physical and biological characteristics from their parents through heredity. The study of heredity is a branch of science called genetics. Within living cells, tiny biochemical structure called DNA carries genetic information. DNA consists of segments, called genes, that carry instructions for the construction and functioning of every aspect of an organism. During cell divisions, random events called mutations can change the sequence of genes and lead to new characteristics and traits. This in turn drives evolution of life, leading to organisms that are better adapted to their environment.