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Introduction to Quantitative Genetics

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Estimating Offspring Phenotype

To estimate the offspring phenotype from the cross of two parents selected
from a base population you need several population parameters.

T = population mean

T_{F} = mother phenotypic value

T_{M} = fathers phenotypic value

T* = midparent value = (T_{F} +
T_{M})/2

*h*^{2} = narrow sense heritability estimate

T_{o} = predicted offspring value

**Formula for predicted offspring value**: T_{o} = T +
*h*^{2}(T* - T)

If T_{F }= IQ of 120 and T_{M} = IQ of 110, then

T* = (120 + 110)/2 = 115

How do the parents deviate from the population?

T*- T = 115- 100 = 15

How much of this deviation is heritable?

*h*^{2}(T* - T) = 0.4(15) = 6

How will the offspring deviate from the population?

T_{o} = T + *h*^{2}^{ }(T* - T) = 100 + 6 =
IQ of 106

**This is the estimate of the offspring phenotype.**