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Livestock Breeding and Genetics > Exam 5 > Flashcards

Exam 5 Flashcards

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1
Q

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

A

Greater-Positive assortative

Less-Negative Assortative

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2
Q

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

A

Crossbreeding

Outbreeding

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3
Q

Define phenotypic, genetic and environmental correlations.

A

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

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4
Q

What is meant by “correlated response to selection”

A

Genetic change in one or more from selection for another trait

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5
Q

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

A

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

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6
Q

Define pleiotropy.

A

Single mutations-has an effect on 2 or more traits

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7
Q

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

A

Must be a trait that affects you economically.

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8
Q

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

A

Truncation- Fast progress on one trait

ICL- more than one trait, less intensity

Both set thresholds for traits

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9
Q

Define random mating, positive and negative assortative.

A

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

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10
Q

Differentiate between random mating and random selection.

A

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.

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11
Q

Does inbreeding increase the proportion of heterozygous or homozygous loci?

A

Homozygous

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12
Q

Define inbreeding depression.

A

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

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13
Q

Compare and contrast inbreeding coefficient and relationship coefficient.

A

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

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14
Q

Compare and contrast identity by descent and identity by state.

A

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

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15
Q

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

A

Decrease

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16
Q

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

A

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

17
Q

Define an economically relevant trait.

A

Brings producer profit

18
Q

What is the difference between positive and negative genetic correlation?

A

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

19
Q

What is the difference between favorable or unfavorable?

A

Producers want favorable-change will be faster

unfavorable is unwanted and has slower genetic change

20
Q

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

A

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

21
Q

What 2 things cause genetic correlations?

A

Pleiotropy and Linkage

22
Q

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

A

Economic Selection-Fastest
Independent Culling levels
Tandam-Slowest

23
Q

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

A

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

24
Q

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

A

Unfavorable

25
Q

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

A

Loss of selection intensity

26
Q

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

A

Its affects GCV

As heterozygosity decreases so will the GCV

27
Q

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

A

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

28
Q

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

A

Tandam- Easy
-Slowest genetic change

Independent culling methods- flexible
-miss out on valuable animals

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

29
Q

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

A

y=calculate an EBV vs. SI$

30
Q

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

A

BV-Genetic value of one trait

SI- Animals genetic value for multiple traits

31
Q

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

A

Economic Selection Index

32
Q

Research Q-$Weaned Calf

A

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

Livestock Breeding and Genetics (5 decks)

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