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.

• The greater the heritability of a condition or trait, the greater is the value of genetic factors in said trait.

Methods

• 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 :

• • 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.

Importance of assessment in medicine

• 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.