Heredity can influence behavior in many ways, with one such example being how color is processed in the brain; color blind people perceive the world in an alternative way, which can cause changes in how everyday tasks are approached. Color perception is directly linked to genes, which illustrates just one way heredity can affect human behavior.
While heredity is certainly one factor that can dictate behavior, it is thought to be closely associated with the effects of environment as well.
Isolating exact behavior changes or patterns to genes is problematic due to the fact that it is highly unethical and immoral to conduct genetic experiments on humans in order to gain scientific evidence. That said, through the study of genetics and human biology there are alternative ways to observe genetic effects on behavior to some extent.
Genetic mutations in the retina provide the strongest evidence that genes influence behavior, and while it is logical to assume that the same could be said for other mutations, there is no credible evidence to suggest that other mutations have the same effect on human behavior.
Environment can have a profound affect on genes themselves, with genetic expression changing as a result of environmental conditions. As such, it is very difficult to identify whether genes or environment have precedence when analyzing the causes of behavior change.