Table 1.

Degrees of genetic causality and power of molecular genetic diagnostics in recessive, dominant and polygenic diseases.

	Monogenic		Polygenic
	Recessive	Dominant
Genetic causality	Strong	Intermediate	Weak
Penetrance	Full	Sometimes incomplete	Weak
Predictive power of mutation analysis	Almost 100%	Stronga	Weak
Age of onset	Fetus, child, adolescent	Adult	Adolescent, adult
Molecular genetic approaches	Direct exon sequencing of known disease genes	Direct exon sequencing of known disease genes	Only assignment of relative risk possible
Frequency	<1:40,000 (rare)	<1:1,000 (rare)	<1:5 (frequent)
Data usually derived from	Gene mapping and gene identification	Gene mapping and gene identification	Genome wide association studies (GWAS)
Confirmation by animal model	Very feasible	Feasible	Difficult

^aExcept for incomplete penetrance and variable expressivity