Exam 4 Flashcards
Heritability can be defined as a ratio of what two variance components?
BV and Phenotype
Repeatability can be defined as a ratio of what two variance components?
Phenotype and Producing ability
Give an example of a trait with low, moderate and high heritability.
Low-Fertility
Moderate-Milk Yield
High- Marbling
List two ways to increase heritability and repeatability. How would this benefit a producer?
1) treat all animals the same way
2) record more data on individual animals
This helps improve selection accuracy
What range of values is possible for heredity?
0-1
Define contemporary group.
A group of animals of the same gender, about the same age and managed the same way
Define heritability.
Regression BV on P
What is an important use for heritability?
Makes selection decisions for traits
Why does the regression coefficient increase as the number of records increase?
It decreases environmental variation
What is the essential principle involved in the several approaches to increasing heritability and repeatability?
Decrease environmental variation
Why do we use adjustment factors?
Increase accuracy of breeding value predictions
Heritability as regression coefficient looks like?
h^2= cov(P,BV)
————-
6^2p
Heritability as a correlation coefficient looks like?
h^2= cov (BV,P)
————-
6BV 6P
In what region of the graph are true breeding values under estimated?
Above the line
Explain why heritability for a trait is not always constant among different groups.
1) Genetic variation of BV
2) Environmental variation
Why should producers use contemporary groups when possible?
Increase accuracy for BV predictibility
Why would livestock producers calculate ratios of trait values?
Easier to tell which animals are above or below average for a trait
Provide one reason why data on all producers animals should be reported to breed associations.
Increase accuracy
What are the four factors that affect genetic gain in a herd or breed?
Selection Intensity
Selection accuracy
Genetic interval
Genetic Variation
Why is the two path version of the genetic change equation usually more appropriate than the one path version? Why?
1) Two path accounts for selection accuracy
2) Selection intensity
3) Generational interval
Different between male and female
What quality in genetic change equation is measured by the correlation between true breeding vales and estimated breeding values?
Selection accuracy
With truncation selection, the selection intensity can be found found in a table. what piece of information is needed to find appropriate selection intensity?
% animals kept as replacements
List two tradeoffs of the key equation.
1) Selection accuracy and genetic interval increase together
2) Selection intensity and generational interval increase together
List three ways that can be used to increase accuracy of a breeding value.
1) Increase Heritability
2) DNA test
3) # of records
What are 2 general methods for predicting breeding values?
Animals performance
DNA testing
What does is mean when we say the EBV is unbiased?
The estimate could go in a favorable or unfavorable way
Why is BLUP more commonly used in breed associations?
1) Genetic trends
2) Contemporary groups
3) Non random breeding
