Exam 5 Flashcards
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?
Crossbreeding
Outbreeding
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?
Homozygous
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?
Decrease
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
Heritability
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
Tandam-Slowest
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?
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
Factor
Birth Weight, Weaning Weight, Maternal Milk, Maternal Cow Size
Why?
Shows the economic impact of the calfs life between bith and weaning.
