Hap Map Project - Bgbunict.it

Genetic and environmental contributions to monogenic and
complex disorders
(A) Monogenic disease. A variant in a single gene is the primary determinant of a
monogenic disease or trait, responsible for most of the disease risk or trait variation
(dark blue sector), with possible minor contributions of modifier genes (yellow
sectors) or environment (light blue sector).
(B) Complex disease. Many variants of small effect (yellow sectors) contribute to
disease risk or trait variation, along with many environmental factors (blue sector).