Falconer's formula

Falconer's formula is a mathematical formula that is used in twin studies to estimate the relative contribution of genetics vs. environment to variation in a particular trait (that is, the heritability of the trait) based on the difference between twin correlations.[1] It was first proposed by the Scottish geneticist Douglas Falconer.[2]

The formula is

Hb2 = 2(rmz - rdz)

where Hb2 is the broad sense heritability, rmz is the (monozygotic, MZ) identical twin correlation, and rdz is the (dizygotic, DZ) fraternal twin correlation. The correlation of same sex MZ twins is always higher than the DZ twin correlation with various sexes and thus all gender differences are evaluated as heritable. To avoid this error, only genetic studies comparing MZ twins with the same sex DZ twins are valid. Correlations between A = hb2 (additive genetics) and C (common environment) must be included in the derivation shown below.

rmz = A + C + 2 Corr(A,C)
rdz = ½A + C + 2 Corr(½A,C)

See also
  • Quantitative genetics

References
  1. Weber WW (2008). "Chapter 5: Genetics in Pharmacology: Twin Studies". Pharmacogenetics (2nd ed.). Oxford: Oxford University Press. pp. 107–8. ISBN 978-0-19-971216-8.
  2. Falconer DS, Mackay TF (1998). Introduction to quantitative genetics (4th ed.). Essex: Longman Group, Ltd. ISBN 978-0-582-24302-6.


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