Heritability, methods and importance of its assessment in medicine

Heritability
 * Heritability is defined as the proportion of the total phenotypic variance of a condition that is caused by additive genetic variance.
 * Often described as h^2.
 * Expressed as either proportion of 1 or percentage.

Methods
 * The greater the heritability of a condition or trait, the greater is the value of genetic factors in said trait.
 * Can be calculated as correlation coefficient, using statistics of normal distribution.
 * Also can be calculated data on the concordance in monozygotic and dizygotic twins.
 * Phenotypic variance
 * Represented by Vp.
 * Components of the phenotypic variance :

Importance of assessment in medicine
 * Vg - genetic variance.
 * Ve - environmental variance.
 * Vge - genetic environmental interaction variance. Vp = Vg + Ve + Vge
 * Vg components :
 * Va - additive genetic variance.
 * Vd - dominance genetic variance.
 * Vi - genic interaction variance. Vg =Va + Vd + Vi  Summary equation  Vp = Va + Vd + Vi + Ve + Vge
 * This equation provides us with a model that describes the potential causes of differences that are  observed among individual phenotypes.
 * In practice, it is desirable to derive heritability estimates using different types of relatives, both that live in the same environment and not.
 * This is important to make sure no environmental factors cloud the result.