Exam 3 Flashcards
What are causes of correlated response?
Linkage
Pleiotropy
What is linkage?
Major genes affecting two traits that are closely linked
Why is linkage considered temporary?
Because of recombination
What is pleiotropy?
Gene influences more than one trait
What is pleiotropy a major cause of?
Halothane gene–HYPP
What do correlated response to selection result from?
Genetic correlations between traits
What are the 3 types of correlation?
Genetic
Phenotypic
Environmental
What does genetic correlation measure?
The relative importance of pleiotropic effects on 2 traits
What is the symbol for genetic correlation?
r_BVx, BVy
What does phenotypic correlation measure?
The strength of the relationship between performance of one trait and performance of another
What is the symbol for phenotypic correlation?
r_Pbw, Pyw
What is environmental correlation a measure of?
The strength of the relationship between environmental effects of one trait and environmental effects of another
What is the symbol for environmental correlation?
r_Ebw, Eyw
What are higher weaning and yearling weights generally associated with?
Higher birth weights
What are higher growth rates generally associated with?
Larger scrotal circumferences and ribeye areas
What are higher growth EPDs generally associated with?
Lower maternal milk EPDs
What are higher maternal milk EPDs generally associated with?
Higher marbling in progeny
What are factors affecting correlated response?
Correlation between traits h^2 i σp (phenotypic variation) L
What is the formula for rate of genetic change?
(r_BVx,BVy x hx x hy x i_x x σpy) / L
READ CHAPTER 13
READ CHAPTER 13
What are the 2 methods of multiple trait selection?
Tandem selection
Independent culling levels
What is tandem selection?
Selection for one trait then another
What is the selection target in tandem selection?
Optimal level needed to be reached
What do you need to be carful of in tandem selection?
Genetic correlations
What is the independent culling levels method of selection?
Minimum standards for traits undergoing multiple trait selections
Allows you to select simultaneously for more than one trait
What does the economic selection index predict?
The aggregate breeding value from multiple trait selections
What is the equation for aggregate breeding value?
H = v1BV1 + v2BV2+…. vmBVm
What is the phenotypic selection index?
A form of economic selection index used with phenotypic selection
What is the equation for phenotypic selection index?
I = b1x1 + b2x2+…..
READ CHAPTER 14
READ CHAPTER 14
What is backcrossing?
The mating of a hybrid to a purebred of a parent breed or line
What is grading up?
Mating system used to create purebred population or convert one breed to another
READ CHAPTER 15
READ CHAPTER 15
What happens in random mating?
Mates chosen at random
All matings are equally likely to occur
Gate cutting, assigning numbers
Where is random mating popular?
Commercial operations
What is random mating best for?
Sire evaluations
What is assortative mating?
Planned matings
What matings occur in assortative?
Mating of similar or dissimilar individuals
Is assortative less or more difficult that random mating? Why?
More difficult
Multiple traits
What are the 2 types of assortative breeding?
Positive
Negative
What is positive assortative breeding?
Best animal to the best animal Creates more variation Increases genetic variation Produces extreme individuals Decreases uniformity
What is negative assortative breeding?
Best animal to the worst animal Decrease variation Produce more intermediates Reduce extreme individuals Increase uniformity
What does negative assortative correct?
Progeny faults
What are 2 different types of negative assortative breeding?
Complementarity matings
Crossbreeding
What are complementarily matings?
Matings of individuals with different but complementary breeding values
What is the overall performance of offspring like in complementarity matings?
It is superior to the average of parents
READ CHAPTER 16
READ CHAPTER 16