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1. Quantitative -weights
traits -heights
-litter size
-number of eggs
-racing speed
controlled by many pairs of genes
2. Genetic effects -Additive effects
-Dominance effects
-Epistatic Effects
3. If a trait is •Because every added desirable gene has a direct impact on the expected phe-
controlled by notype
many pairs of
genes with addi-
tive gene action,
it will be easier
to make improve-
ment through se-
lection
4. Epistasis Interaction among genes at multiple loci
5. Subdivision of en- -Temporary environment effects
vironmental com-
ponents -Permanent environmental effects
6. If there is a nor- There is a normal distribution of:
mal distribution
of phenotypes -Additive effects
-Dominance effects
-Epistatic effects
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, ANSC 4395 Exam 4
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-Permanent environmental effects
-Temporary environmental effects
7. Heritability •The proportion of the phenotypic variation which is due to additive gene effects
-The most important single concept in animal breeding
-In general it tells us how easy it is to make improvements through selection
-varies from herd to herd
-Varies with any herd if management changes
8. The importance -Compensates for the low heritability
of reproductive
traits -Should be included in most selection programs
9. Phenotypic Cor- •Association between actual performance for 2 traits
relation
-Has both a genetic and environmental contribution
-WW and ADG =.20
10. Genetic Correla- •Association between genetic merit for two traits
tion
-Some genes contribute to more than one trait
-WW and ADG =.46
-Allows it to evaluate "indirect" effects of selection
11. Selection The practice of allowing certain individuals more opportunity to reproduce than
others
12. Results of selec- Predictable in magnitude and direction but prediction is only as good as the
tion information
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