Exam 4

Question 1

Heritability can be defined as a ratio of what two variance components?

Answer 1

BV and Phenotype

Question 2

Repeatability can be defined as a ratio of what two variance components?

Answer 2

Phenotype and Producing ability

Question 3

Give an example of a trait with low, moderate and high heritability.

Answer 3

Low-Fertility
Moderate-Milk Yield
High- Marbling

Question 4

List two ways to increase heritability and repeatability. How would this benefit a producer?

Answer 4

1) treat all animals the same way
2) record more data on individual animals
This helps improve selection accuracy

Question 5

What range of values is possible for heredity?

Answer 5

0-1

Question 6

Define contemporary group.

Answer 6

A group of animals of the same gender, about the same age and managed the same way

Question 7

Define heritability.

Answer 7

Regression BV on P

Question 8

What is an important use for heritability?

Answer 8

Makes selection decisions for traits

Question 9

Why does the regression coefficient increase as the number of records increase?

Answer 9

It decreases environmental variation

Question 10

What is the essential principle involved in the several approaches to increasing heritability and repeatability?

Answer 10

Decrease environmental variation

Question 11

Why do we use adjustment factors?

Answer 11

Increase accuracy of breeding value predictions

Question 12

Heritability as regression coefficient looks like?

Answer 12

h^2= cov(P,BV)
————-
6^2p

Question 13

Heritability as a correlation coefficient looks like?

Answer 13

h^2= cov (BV,P)
————-
6BV 6P

Question 14

In what region of the graph are true breeding values under estimated?

Answer 14

Above the line

Question 15

Explain why heritability for a trait is not always constant among different groups.

Answer 15

1) Genetic variation of BV

2) Environmental variation

Question 16

Why should producers use contemporary groups when possible?

Answer 16

Increase accuracy for BV predictibility

Question 17

Why would livestock producers calculate ratios of trait values?

Answer 17

Easier to tell which animals are above or below average for a trait

Question 18

Provide one reason why data on all producers animals should be reported to breed associations.

Answer 18

Increase accuracy

Question 19

What are the four factors that affect genetic gain in a herd or breed?

Answer 19

Selection Intensity
Selection accuracy
Genetic interval
Genetic Variation

Question 20

Why is the two path version of the genetic change equation usually more appropriate than the one path version? Why?

Answer 20

1) Two path accounts for selection accuracy
2) Selection intensity
3) Generational interval
Different between male and female

Question 21

What quality in genetic change equation is measured by the correlation between true breeding vales and estimated breeding values?

Answer 21

Selection accuracy

Question 22

With truncation selection, the selection intensity can be found found in a table. what piece of information is needed to find appropriate selection intensity?

Answer 22

% animals kept as replacements

Question 23

List two tradeoffs of the key equation.

Answer 23

1) Selection accuracy and genetic interval increase together

2) Selection intensity and generational interval increase together

Question 24

List three ways that can be used to increase accuracy of a breeding value.

Answer 24

1) Increase Heritability
2) DNA test
3) # of records

Question 25

What are 2 general methods for predicting breeding values?

Answer 25

Animals performance

DNA testing

Question 26

What does is mean when we say the EBV is unbiased?

Answer 26

The estimate could go in a favorable or unfavorable way

Question 27

Why is BLUP more commonly used in breed associations?

Answer 27

1) Genetic trends
2) Contemporary groups
3) Non random breeding