Multifactorial traits:
Traits determined by genes and the environment
Polygenic traits:
Individual genes follow Mendel's laws, but effect of one gene is additive (more than one gene determines phenotype)
Twin Studies:
MZ twins (monozygotic twins): have the same genotype
DZ twins (dizygotc twins): share as many genes as normal siblings
If you wach the development of MZ twins, who have the same genotype and should herefore be identical, you can see how the environment influences their traits to be different.
Example for multifactorial traits:
Narcolepsy
Symptoms:
-affected person falls asleep several times a day
-sleep paralysis
-cataplexy
environmantal factors:
-infection
-brain injuries
-autoimmune disorders
-low level of histamine
-environmental toxins
