Number of phenotypes to number of genes involved relationship
2n+1
Relationship between number of genes and proportion of individuals who can be found on either extreme?
the ends decrease
What is the phenotypic variance equation?
VP = VG + VE
VG: variance explained by genetics
VE: variants explained by environment
Threshold of liability
the transition from unaffected to affected in genetic liability
Variance
a measure of how much the values in a data set differ from the mean
SUM ((x-avg)^2/df)
df = sample size - 1
Standard deviation
square root of the variance. How much individual data points deviate from the mean
Broad-sense heritability (H2)
H2 = VG/VP
Estimates the proportion of phenotypic variation that is due to total genetic variation
Narrow sense heritability (h2)
h2 = VA/VP
Proportion of phenotypic variation that is due to additive genetic variation
Assumptions of broad sense heritability for mono and dizygotic twins
- equal environment assumption
- stronger maternal effects in mz than dz
- greater similarity in interactions between genes and environment in mz than dz
all three overestimate VG
pure parental breeding lines equation
VP = VE
Genetically uniform F1 eq
VP = VE
Genetically diverse F2 eq
normal VP equation
Breeder’s equation
R = h2S
R: change in the mean of the next gen
S: how far the selected parents are from the population mean
Attributes of heritability
- measure of the degree to which genetic differences contribute
- accurate only for the environment and population in which they are measured
- heritability for a given trait can change
- high heritability does not preclude environmental factors
