Exam 2

Question 1

The Key Equation

Answer 1

The equation relating the rate of genetic change resulting from selection to four factors.

Question 2

The four factors of the key equation

Answer 2

Accuracy of selection, selection intensity, genetic variation, and generation interval

Question 3

Rate of Genetic Change

Answer 3

Rate of change in the mean breeding value of a population. Also called the response to selection

Question 4

True or false. Crossbreeding and Inbreeding are not transferable to offspring.

Answer 4

True

Question 5

Accuracy of selection

Answer 5

A measure of the strength of the relationship between true breeding value and their predictions for a trait under selection

Question 6

True or false. The higher the heritability the more accurate we are in selection.

Answer 6

True

Question 7

Selection criterion

Answer 7

Information that selection decisions are based on. Also called predictions

Question 8

What are some values that are apart of selection criterion?

Answer 8

EBV, EPD, phenotypic selection, and scientific guess

Question 9

Selection intensity

Answer 9

A measure of how choosy breeders are in deciding which individuals are selected

Question 10

If intensity is high assuming selection criterion are reasonably accurate…

Answer 10

parents should be a lot better than average, offspring should be extremely better than average, rate of change should be rapid

Question 11

If intensity is low…

Answer 11

parents are about average, offspring will also be about average

Question 12

Truncation selection

Answer 12

selection on the basis of a distinct division in the selection criterion above which individuals are kept and below which they are rejected. the more animals kept the lower the intensity

Question 13

proportion saved

Answer 13

the number of individuals chosen to be parents as a proportion of the number of potential parents

Question 14

effective proportion saved

Answer 14

in selection - a value that, when substituted for actual proportion saved reflects correct selection intensity

Question 15

threshold traits

Answer 15

polygenic traits that are not continuous in their expression but exhibit categorical phenotypes. selection intensities tend to be small

Question 16

true or false. the better the performance of a population in a threshold trait the smaller the selection intensity

Answer 16

true

Question 17

true or false. The more thresholds you have the closer you are to a continuous trait

Answer 17

true

Question 18

genetic variation

Answer 18

variability of breeding values within a population for a trait under selection

Question 19

characteristics of a large genetic variation

Answer 19

selection is intense, selection criteria is reasonably accurate, the best animals are far superior to average, fast rate of genetic change

Question 20

genetic interval

Answer 20

the amount of time required to replace one generation with the next

Question 21

genetic trend

Answer 21

the change in the mean breeding value of a population over time

Question 22

replacement rate

Answer 22

the rate at which newly selected individuals replace existing parents in a population

Question 23

selection risk

Answer 23

the risk that true breeding values of replacements will be significantly poorer than expected

Question 24

breeding value lag

Answer 24

over time the genetic trend in the offspring will be the same as the genetic trend of the sire, the amount of time that is required for this to happen is the breeding value lag

Question 25

quanititative genetics

Answer 25

the branch of genetics concerned with influences on measurement of relationships among genetic prediction for and rate of change in traits that are or can be treated as quantitative

Question 26

phenotypic value

Answer 26

measure of performance for a trait in an individual

Question 27

genotypic value

Answer 27

effect of an individuals genes on its performance for a trait

Question 28

enviromental effect

Answer 28

effect that external factors have on animal performance

Question 29

population mean

Answer 29

the average phenotypic value of all individuals in a population

Question 30

breeding value

Answer 30

the value of an individual as a genetic parent. important for selection

Question 31

independent gene effect

Answer 31

the effect of a gene independent of the effect of the other gene at the same locus and the effects of genes at other loci

Question 32

progeny difference

Answer 32

half an individuals breeding value - the expected difference between the mean performance of the individuals progeny and the mean performance of all progeny

Question 33

gene combination value

Answer 33

the part of an individuals genotypic value that is due to the effects of gene combinations and therefore cannot be transferred from parents to offspring. cannot be passed to offspring. important for contribution to animal performance

Question 34

gene combination value is not transferable to progeny, but has a great impact on individuals performance in

Answer 34

hybrid vigor and inbreeding depression

Question 35

producing ability

Answer 35

the function of all factors that permanently affect an individuals performance potential. important for repeated traits

Question 36

repeated trait

Answer 36

a trait for which individuals commonly have more than one performance record. ex. milk production, weaning wt, twining in sheep

Question 37

what values are determined at conception

Answer 37

genotypic values, breeding values, and gene combination values

Question 38

permanent enviromental effects

Answer 38

permanently impact the animals performance. combo of genetic and environment

Question 39

temporary environmental effects

Answer 39

temporary impact on animals performance. purely environment

Question 40

heritability

Answer 40

a measure of the strength of the relationship between performance and breeding values for a trait in a population

Question 41

repeatability

Answer 41

a measure of the strength of the relationship between repeated records for a trait in a population

Question 42

contemporary group

Answer 42

a group of animals that have experienced a similar environment with respect to the expression of a trait

Question 43

trait ratio

Answer 43

an expression of a relative performance - the ratio of an individuals performance to the average performance of all animals in the individuals contemporary group

Question 44

normal distibution

Answer 44

individual values tend to follow a set of distribution within a population. symmetric, bell shaped curve, vertical axis

Question 45

mean

Answer 45

an arithmetic average

Question 46

variation

Answer 46

differences among individuals within a population

Question 47

standard deviation

Answer 47

an average deviation from the mean

Question 48

flat curve =

Answer 48

large amount of variation

Question 49

sharp steep curve =

Answer 49

less variation

Question 50

68%

Answer 50

within one standard deviation

Question 51

95%

Answer 51

within 2 standard deviation

Question 52

99%

Answer 52

within 3 standard deviation

Question 53

covariation

Answer 53

how two traits or values vary together in a population

Question 54

positive covariation move in the...

Answer 54

same direction

Question 55

negative covariation move in the...

Answer 55

opposite direction

Question 56

what are the two aspects of covariation

Answer 56

direction and strength

Question 57

correlation

Answer 57

a measure of the strength of the relationship between two variables

Question 58

regression

Answer 58

the expected or average change in one variable per unity change in another