Genetics determines our mental and physical characteristics. It is genes that specify that we are human and we cannot breathe under water or fly, but we can learn how to speak and write. Genes determines why some people are born with average intelligence, others absolute memory and others with absolute music hearing.
Genes determines a lot of our inclinations and traits. Girls have tendency to deal with dolls, instead of machines. They affect how we react to certain diseases and certain activities. It is important to remember that people are continuously pushed by certain tendency. Propensity is made by the genes and individual are responsible for the behaviour.
Kindness to aggression, dementia to brilliance, extroversion or autism is transmitted from a parent to a child. Whether a person can be taught or not, it also associated to his genetics. Simply put, genes are carriers of all our capabilities. Environment only play an insignificant role on the character of a parson.