Quantitative genetics - week 4 Flashcards
examples of quantitative genetics
milk yield
speed
lameness
growth rate
what are quantitative traits affected by
loci, each with small effects - infinitesimal model
what % of the population of animals do we expect to find in the first standard deviation
68%
95% - 2 standard deviation from mean
99.7% - 3 standard deviation from mean
what does a narrow distribution say?
less variation
what slows down improvement in the population
the less variation in your populations the slower it is to make an improvement
what is the bulmer effect
reduction in variations due to selection programme
what are threshold traits
discrete (qualitative )on phenotypic scale. can be described as a 1 or 0 or yes or no
but also continuous (quantitative) on genetic scale
example:
pregnancy
why are threshold traits less accurate
due to challenges in classifications
what traits do you look at when calculating accuracy of estimation
qualitative traits - accuracy is expressed as a probability of a normal animal being a carrier of the deleterious gene
Quantitative trait - accuracy is estimated as the correlation between estimated and true genotype
Threshold Trait - same as quantitative but less accurate due to fuzzy observation
equation for Phenotype
phenotype = genotype + environment
P = G+E
equation for Genotype
Genotype = Additive + Non - additive (cannot predict what will be inherited from offspring to parent)
G= A+NA
what is the equation for environment
Environment= Perament Environment (may affect animal for more than 1 life cycle/mastitis) + Temporary Environment (poor quality silage)
E = Ep +Et
symbol for variation
stigma sq
what can have a major impact on environment
phenotype
what can happen if we dont accurately account for environment
major impact on evaluating how the genotype affects the phenotype
what is the simplest method to control the environmental component
contemporary group
what are contemporary groups
a group of animals with equal opportunity to perform
example : horse race
- all run at same time and place
- usually same age
what is correlation
measure of the strength of the relationship between two variables
what does correlation range from
range from -1 to 1
- no correlation = 0
- negative correlation < 0
- positive correlation > 0
what is phenotype correlation
measure of the strength of relationship between performance in one trait and performance in another
what is genetic correlation
measure of the strength of relationship between breeding values in one trait and breeding values in another
what is environmental correlation
measure of the strength of relationship between environmental effects in one trait and environmental effects in another
what is breeding value
the average transmittable genetic effect of an individual for a trait
what have bulls a BV for
milk yield
