Term
| 2 properties of a trait of economic importance in a population |
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Definition
1: heritability
2: phenotypic variability |
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Term
| when genetic improvement is almost impossible |
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Definition
| When a trait is not heritable or has no variability |
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Term
| 2 ways a breeder can change a population |
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Definition
1. Choice of individuals used as parents through artificial selection.
2. Control the way by which parents are mated (mating plan). |
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Term
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Definition
| Choice of individuals used as parents |
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Term
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Definition
| Controlling the way by which parents are mated |
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Term
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Definition
| The genetic change due to selection |
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Term
| Response to selection (R) |
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Definition
| the difference in mean phenotypic value between offspring of the selected parents and the whole parental generation before selection. |
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Term
| Selection differential (S) |
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Definition
| the mean value of the selected individuals selected as parents expressed as a deviation from the population mean. |
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Term
| how to calculate Response to selection (R) |
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Definition
| R = h2 * S
h2 = heritability
S = Selection differential |
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Term
| The selection differential can be predicted in advance when these 2 conditions are met |
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Definition
1: The phenotypic value of the trait under selection is normally distributed.
2: Selection is by truncation. |
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Term
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Definition
| individuals being chosen strictly in order of merit as judged by their phenotypic values |
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Term
| under the previously mentioned conditions, selection differential depends on... |
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Definition
| 1: The proportion of the population selected, p
2: The phenotypic standard deviation of the trait, σp |
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Term
| standardized selection differential |
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Definition
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Term
| how to calculate intensity of selection (i) |
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Definition
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Term
| how to calculate Response to selection (R) when intensity of selection is factored in |
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Definition
| R = i h2 σP
or
R = i h σA
or
R = (i h σA) / L
h = accuracy of selection
L = generation interval |
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Term
| Response to Selection depends on |
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Definition
1. Selection Intensity
2. Heritability of the Trait
3. Variability in the Trait |
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Term
| sources of correlation among traits |
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Definition
-genetic factors
-environmental factors |
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Term
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Definition
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Term
| genetic cause of correlation |
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Definition
| mostly pleiotropic property of genes |
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Term
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Definition
| propensity of a gene to affect more than one trait |
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Term
| when the environment causes correlation among traits |
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Definition
| when two traits are influenced by the same differences in environmental conditions |
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Term
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Definition
| response to the selection of a particular trait, such as trait X |
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Term
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Definition
| the changes you observe on a trait other than the one you selected for; in this case, observed for trait Y when you selected for trait X. it can go the other way around as well. |
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Term
| how to calculate direct response |
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Definition
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Term
| how to calculate correlated response |
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Definition
| CRY = i hX hY rg σPY
rg = genetic correlation between traits X and Y |
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Term
| Advantages of Indirect Selection |
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Definition
1: Trait X is cheaper and easier to measure
2: Trait X can be measured earlier in life
3: Trait Y is sex-limited, but trait X can be measured in both sexes.
4: A typical example would be carcass trait. |
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Term
| some things to be considered in the optimization of a breeding program |
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Definition
-genetic variance
-accuracy of selection
-intensity of selection
-generation interval
-population size |
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Term
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Definition
| selection causing reduction of additive genetic variance in the parents |
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Term
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Definition
| the correlation between the selection criteria and the true breeding value for the breeding goal that is to be improved |
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Term
| when selection intensity is directly related to the number of animals selected |
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Definition
| When the distribution of a trait is normal and selection is by truncation |
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Term
| selection intensity vs. response to selection |
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Definition
| increased selection intensity improves response to selection |
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Term
| selection intensity can be limited by |
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Definition
1: reproductive capacity of the selected individuals
2: population size
3: inbreeding |
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Term
| selection intensity vs. effective population size |
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Definition
| greater intensity leads to smaller effective population size |
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Term
| accuracy of selection vs. effective population size |
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Definition
| greater accuracy of selection reduces effective population size due to relatives being selected |
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Term
| Most selection schemes aim at... |
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Definition
| optimizing the factors that affect rate of genetic gain |
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Term
| The objective in optimized breeding strategies needs to be... |
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Definition
| maximizing genetic gain while restricting inbreeding |
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Term
| The factors that affect annual response to selection |
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Definition
-genetic variance
-accuracy of selection
-intensity of selection
-generation interval
-population size |
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Term
| what increasing selection intensity does for inbreeding |
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Definition
| leads to rapid genetic gains, but also increases inbreeding |
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Term
| disadvantage of selecting young animals |
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Definition
| they have less information available |
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Term
| To optimize long term selection, it is useful to... |
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Definition
| combine selection on BLUP EBV with some restriction on the average relatedness of the selected animals |
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Term
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Definition
| Best Linear Unbiased Prediction of breeding value |
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Term
| Selection by definition implies... |
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Definition
| lack of opportunity for all members of the population to mate |
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Term
| Non-random mating leads to... |
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Definition
| disequilibrium (non-random association of alleles) |
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Term
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Definition
| non-random association of alleles |
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Term
| effect of disequilibrium (non-random association of alleles) |
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Definition
| reduces the genetic variance |
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Term
| how to calculate theoretical maximum response (Rmax) |
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Definition
| Rmax = 2Neih2σp
Ne = effective population size |
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Term
| some factors that affect long term selection limits |
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Definition
-Disequilibrium
-Inbreeding (genetic drift)
-Natural Selection
-Number of loci
-Physiological constraints |
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Term
| some natural selection factors that can affect long term selection limits |
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Definition
-Fertility
-Selection differential
-Favoring heterozygotes |
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Term
| selection limit can be broken by... |
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Definition
-Relaxing selection followed by selection
-Mutations to generate “new” additive genetic variation |
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Term
| how the poultry industry maintains its populations |
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Definition
-Primary breeders maintain large populations in replicates
-Primary breeders limit the level of inbreeding per generation
-Geneticists practice multi-trait selection with different weights on different traits.
-Industrial lines can also benefit for mutations |
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Term
| advantage of multi-trait selection |
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Definition
it does not exhaust genetic variance as much as selecting on a single trait
This can potentially ensure existence of genetic variation for many generations to come. |
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