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Flashcards in Exam 5 Deck (32):

Which type of mating strategy will result in greater genetic variation and less genetic variation?

Greater-Positive assortative
Less-Negative Assortative


What are two strategies that can be used to reduce the effects of inbreeding depression in a herd assuming inbreeding is a problem?



Define phenotypic, genetic and environmental correlations.

Phenotypic- measure of the strength of the relationship between Performance of two traits.

Genetic-measure of the strength of the relationship between BV of two traits

Environmental- Correlation between two Environmental traits


What is meant by "correlated response to selection"

Genetic change in one or more from selection for another trait


Define indicator trait and provide an example of an indicator trait in the livestock industry.

A trait that is not important on its own but has a genetic impact on an economically valuable trait. BW impacts Calving Ease


Define pleiotropy.

Single mutations-has an effect on 2 or more traits


What is the main factor that determines whether a trait should be included in a breeding objective.

Must be a trait that affects you economically.


What are the similarities and differences between truncation selection and selection by independent culling levels.

Truncation- Fast progress on one trait

ICL- more than one trait, less intensity

Both set thresholds for traits


Define random mating, positive and negative assortative.

Random-Randomly breeding chosen males and females-not the same as random selection

Positive-Breeding like to like animals-higher chance of superior animals

Negative- Mate like to non-like- increase uniformity


Differentiate between random mating and random selection.

Mating-You have chosen quality sires, you just aren't controlling who each sire individually breeds.

Selection-Any random male will breed with any random female, you didn't choose the genetics.


Does inbreeding increase the proportion of heterozygous or homozygous loci?



Define inbreeding depression.

A decrease of performance as a result of an increase of inbreeding


Compare and contrast inbreeding coefficient and relationship coefficient.

Inbreeding-Single animal- probability that at a locus the two alleles are identical by descent

Relationship-% alleles that are identical between 2 individuals

Both calculate alleles that are identical by descent


Compare and contrast identity by descent and identity by state.

State-two identical alleles at a locus

Descent- two alleles that are identical at a locus that are passed from a common ancestor

Both look over alleles that are identical


Will Selection intensity for a single trait increase or decrease as the number of traits selected for, increase?



What are three reasons why indirect selection on an indicator trait is preferable to direct selection on an economically relevant trait?

1) Indirect is easier to measure
2) Indirect can be measured earlier
3) Indirect has a higher selection accuracy


Define an economically relevant trait.

Brings producer profit


What is the difference between positive and negative genetic correlation?

Positive means the two traits increase or decrease at the same time
Negative is when the two traits go in opposite directions


What is the difference between favorable or unfavorable?

Producers want favorable-change will be faster
unfavorable is unwanted and has slower genetic change


What two variables are involved in each of the correlations below?
Genetic Correlation
Accuracy of EBV

Genetic Correlation- EBV1, EBV2
Accuracy of EBV-EBV and TBV
Heritability- BV, P


What 2 things cause genetic correlations?

Pleiotropy and Linkage


List three methods of multiple trait selection and which has the fastest and slowest genetic change.

Economic Selection-Fastest
Independent Culling levels


Why is the economic selection index considered to be the method of multiple trait selection that can result in the fastest genetic change?

Only method of multiple trait selection that can select for economic value of each trait


When practicing multiple trait selection is the the loss of selection intensity greater when the trait are favorable or unfavorable?



What is one of the main consequences of multiple trait selection in comparison to single trait selection?

Loss of selection intensity


In the basic genetic model genotypic value is composed of two components. Which component is changed due to inbreeding? Why?

Its affects GCV
As heterozygosity decreases so will the GCV


If two alleles at a locus are identical by descent what does this mean?

Two alleles at the same locus are identical and come from a common ancestor


List one advantage and one disadvantage of the three methods of multiple trait selection.

Tandam- Easy
-Slowest genetic change

Independent culling methods- flexible
-miss out on valuable animals

Economically selection Index-Fastest Change
-complex, hard to implement yourself


What is one essential difference between these 2 applications of the selection index technique. Describe using x or y axis.

y=calculate an EBV vs. SI$


What is the difference between a breeding value and a selection index?

BV-Genetic value of one trait
SI- Animals genetic value for multiple traits


$Weaned Calf, $ Cow Energy TPI and Terminal Sire Index are all examples of what method of multiple trait selection?

Economic Selection Index


Research Q-$Weaned Calf

Birth Weight, Weaning Weight, Maternal Milk, Maternal Cow Size
Shows the economic impact of the calfs life between bith and weaning.