Other factors affecting expression
Phenocopy
- an environmental factor triggers an illness that resembles a genetic disease
- eg. deafness due to rubella infection in pregnancy
Environmental effects
- an illness may be exacerbated by the environment, or can be treated by controlling the environment
- eg. Severity of PKU due to amount of phenylalanine in diet
Anticipation
- severity increases with each successive generation
- often can be confused with random variations in severity