Topic 29 Flashcards
Quantitative population genetics
characterizes population traits using phenotypic performances or genomic information; It analyses the genetic determination and the environmental impact on the polygenic train, and measure alteration by time
Quantitative trait
characteristic trait that can be expressed mathematically e.g. milk yield
Regression
gives the measure of the association between the dependent variable and the independent variable(s), usually formulated in an equation in which the independent variable(s) have parametric coefficients
Regression toward the mean
is the phenomenon that if a variable is extreme on its first measurement, it will tend to be closer to the average on its second measurement and paradoxically if it is extreme on the second measurement, it will tend to have been closer to the average on its first
Galton’s regression
Galton observed that extreme characteristics e.g. height in parents aren’t passed on completely to their offspring. The characteristics in the offspring regress towards a mediocre point (mean).
How did Galton experiment?
By measuring the heights if hundreds of people, he was able to quantify regression to the mean and estimate the size of the effect.
What was Galton’s conclusion?
He said that “the average regression of the offspring is a constant fraction of their respective mid parental deviations”. This means the difference between a child and its parents for some characteristic is proportional to the parents deviation from typical people in the population
Heritablity Estimate
a single trait measured on animals in a specific population at any given point in time. Estimates of heritability for a trait can differ between breeds of animals and may change slowly over time
What is heritability a measure of?
It is a measure of the degree (0-100%) to which offspring resemble their parents for a specific trait. This definition can be extended to all genetic relationships such as half sisters sired by the same bull; It measures the strength of the relationship between performance and breeding value of an individual animal; It measures the expected difference in breeding value of an animal for each unit of difference in that animals phenotype for a trait; It is a ratio of causes of variation between animals. Heritability is the percentage of all differences between animals by gene effects that transfer from generation to generation
Heritability (formula)
H2= var(G)/var(P); G=genotype; P=phenotype
Family units most often used to evaluate degree of resemblance include
Parent and offspring; parents and offspring; full siblings; half siblings
Heritability estimates are used for
Breeding value estimation; prediction of selection response; helping decision of selection method; choice of mating period; prognostic of result of crossbreeding
