Genetics is the study of genes and inheritance. It studies how parents pass on to their children different characteristics or traits. Every person inherits half of their genes from the mother and the other half from the father. Still, everyone is unique in a variety of traits, such as height, eye color, health or disease. Therefore, children are in many ways similar but not identical to their parents or their siblings. Most of our traits are determined by a combination of genes and environment (e.g., body weight is caused by genetics and lifestyle).