Falconer's formula
Encyclopedia
Falconer's formula is used in twin studies
to determine the genetic
heritability of a trait
based on the difference between twin
correlation
s.
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. Or correlation between A = hb2 (additive genetics) and C (common environment) must be included in derivation
and can not be neglected (also as covariance
in the statistical model).
It is also possible to do narrow-sense heritability
estimates by using sibling/adoptee correlations:
hn2 = rsib - rad, where hn2 is the narrow sense heritability, rsib is the sibling correlation, and rad is the adoptee correlation.
Twin study
Twin studies help disentangle the relative importance of environmental and genetic influences on individual traits and behaviors. Twin research is considered a key tool in behavioral genetics and related fields...
to determine the genetic
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
heritability of a trait
Trait (biology)
A trait is a distinct variant of a phenotypic character of an organism that may be inherited, environmentally determined or be a combination of the two...
based on the difference between twin
Twin
A twin is one of two offspring produced in the same pregnancy. Twins can either be monozygotic , meaning that they develop from one zygote that splits and forms two embryos, or dizygotic because they develop from two separate eggs that are fertilized by two separate sperm.In contrast, a fetus...
correlation
Correlation
In statistics, dependence refers to any statistical relationship between two random variables or two sets of data. Correlation refers to any of a broad class of statistical relationships involving dependence....
s.
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
Gender differences
A sex difference is a distinction of biological and/or physiological characteristics associated with either males or females of a species. These can be of several types, including direct and indirect. Direct being the direct result of differences prescribed by the Y-chromosome, and indirect being...
are evaluated as heritable. To avoid this error, only genetic studies comparing MZ twins with the same sex DZ twins are valid. Or correlation between A = hb2 (additive genetics) and C (common environment) must be included in derivation
- rmz = A + C + 2 Corr(A,C)
- rdz = ½A + C + 2 Corr(½A,C)
and can not be neglected (also as covariance
Covariance
In probability theory and statistics, covariance is a measure of how much two variables change together. Variance is a special case of the covariance when the two variables are identical.- Definition :...
in the statistical model).
It is also possible to do narrow-sense heritability
Heritability
The Heritability of a population is the proportion of observable differences between individuals that is due to genetic differences. Factors including genetics, environment and random chance can all contribute to the variation between individuals in their observable characteristics...
estimates by using sibling/adoptee correlations:
hn2 = rsib - rad, where hn2 is the narrow sense heritability, rsib is the sibling correlation, and rad is the adoptee correlation.