In addition to affecting development, changing hormone levels affect certain behaviors or traits that are gender dimorphic, such as superior verbal fluency among women.

The genotype of an organism directly and indirectly affects its molecular, physical, and other traits, which individually or collectively are called its phenotype.

A QTL is a region in the genome that affects the trait or traits of interest.

Thus, a change in a pleiotropic immunity or virulence gene may automatically affect other traits.

With the advent of genomic sequencing, it has become possible to search for and identify specific gene polymorphisms that affect traits such as IQ and personality.

A single gene may affect multiple traits.

The T-stock mouse harbors 7 recessive, viable mutations affecting easily recognizable traits.

Multiple genes may simultaneously affect behavioural traits.

Such people might only affect such traits by great difficulty, or they may even be impossible to display.