Response to Selection & Correlated Response Flashcards
What are the four methods of genetic prediction?
- Genomic Selection
- Mass Selection (Individual)
- BLUP
- Selection Index
What does S stand for?
Selection Differential
Define Selection Differential.
Superiority of the parents over the average.
What does R stand for?
Selection Response
Define Selection Response.
The change in the average of a particular trait due to selection for that trait.
What is the Breeder’s Equation?
R = h^2 x S
What are the four factors that affect Selection Response?
- Heritability (h^2)
- Selection Intensity (i)
- Generation Interval (L)
- Accuracy of Selection
Define Accuracy of Selection.
A measure of the strength of the relationship between the true breeding values and their predictions for a trait under selection.
OR
Measures how well the BV of an animal is estimated.
Define Selection Intensity (i).
Represents the mean of the selected proportion in phenotypic standard deviations.
What is the equation for Selection Intensity?
i = S / (phenotypic standard deviation)
High intensity Selection Response causes:
- parents far better than average
- superior offspring
- fast genetic change
Low intensity Selection Response causes:
- parents not much better than average
- offspring will be average
- slow genetic change
Selection response is ______________ related to selection intensity, however the relationship is not ___________.
directly ; linear
How do you find selection intensity without the equation?
Know the percent of the herd that you plan to keep and use the table.
Define generation interval?
Amount of time required to replace one generation with the next.
True or False. Generation interval is the same throughout all species.
False!
As L decreases, accuracy _____________.
decreases
As accuracy increases, i will ______________.
decrease
As i increases, this leads to a _________ replacement rate.
low
Genetic Gain is measured in ____________ per ____________.
units (whatever units of the trait) ; generation
Selections for one trait ________________ affects just that one trait.
rarely
Define correlation.
Measures the strength (consistency and reliability) of the relationship between two variables.
Define phenotypic correlation.
Measures the degree and direction of the relationship between the phenotypes of the two traits.
Define genetic correlation.
Measures the degree and direction of the relationship between the EBVs/PTAs of the two traits.
Define correlated response.
Genetic change in one or more traits (indirect) resulting from selection for another trait (direct).
What are the three causes of genetic correlation?
- GEI
- Linkage
- Pleiotropy
- You should know this!!
What is the major cause of correlated response?
Pleiotropy!
Are correlations for populations or single animals?
They are population measures!
Correlations ________________ fixed and ____________ dependent on the population the measures are in.
are not ; are
Correlation can be classified in three ways, which are:
- degree/strength of relationship
- direction/sign of the relationship
- being favorable or unfavorable
A ____________ genetic correlation does not mean that the relationship is favorable.
positive
True or False. Negative genetic correlation is always bad.
False!
Define direct selection.
Selection for a given trait to improve that same trait.
Define indirect selection.
Selection for a given trait to improve a genetically correlated trait.
Define Indicator trait.
Traits or characters used in indirect selection to improve a genetically correlated trait.
What is the one factor that affects only correlated response to selection?
Genetic correlation
What are the five factors that affect correlated response to selection?
- Heritability (h^2)
- Selection Intensity (i)
- Generation Interval (L)
- Accuracy of Selection
- Genetic correlation
Selection is typically used to (3 responses):
- reach a breeding goal
- improve in a particular direction
- maintain a particular performance level
