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| The most important question about quantitative traits |
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Definition
| whether or not genes influence the observed variation in the trait |
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| comprises of the individual’s genetic value and influences from the environment |
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| all non-genetic influences (diet, housing, disease, management) |
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| some types of environmental factors |
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Definition
-diet
-housing
-disease
-management |
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Term
how to calculate phenotype value (P)
equation for phenotype (P), genotype (G), and environment (E) |
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Definition
Phenotype (P) = Genotype (G) + Environment (E)
phenotype (P) = Allele value (A) + Dominance (D) + Epistasis (I) + environment (E) |
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Term
| the basis for genetic improvement |
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Definition
| differences in genetic values |
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Term
| why the genetic worth of an individual cannot be judged from the phenotypic value |
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Definition
| because phenotypic and genotypic ranking could be different |
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Term
| variation is expressed as... |
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Definition
Variance
phenotype (P) = genotype (G) + environment (E) |
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| how to calculate genotypic value |
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Definition
| Genotype (G) = Allele value (A) + Dominance (D) + Epistasis (I) |
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Term
| variance components and their symbols |
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Definition
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Definition
| The total variance is the variation in the performance for a trait between individuals in a population. |
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Term
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Definition
The variance in the genotypic values for a trait. The genotypic value is the combined effect of...
(1) all the alleles at all loci
(2) intra-loci interactions
(3) inter loci interactions that affect a trait. |
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Term
| Additive Genetic variance, VA |
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Definition
| The variation among alleles transmitted from parents to offspring that affect a trait. The sum of the effect of alleles transmitted from a parent to its offspring for a trait is the Breeding Value (BV) of the parent for that particular trait. |
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Term
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Definition
| The sum of the effect of alleles transmitted from a parent to its offspring for a trait |
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Term
| Dominance Genetic Variance, VD |
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Definition
| Genetic variation that occurs as a result of interaction among alleles at a locus. This effect is not accounted for by the effect of two alleles taken singly. For example, assuming the value of A1 is 2, and value of A2 is 3, however the value of the two alleles combined, A1A2 is 7. The dominance deviation in this case is 7 - (2+3) = 2. The combined effect of the two alleles is not additive. The dominance genetic variance measures the non-additive effect between alleles at a locus. |
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Term
| Epistasis Genetic Variance, VI |
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Definition
| Genetic variation that occurs as a result of interaction among alleles at different loci. This is also the non-additive effect between genes at different loci. |
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Term
| “Non-additive genetic variance” |
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Definition
| dominance and epistasis genetic variations. |
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Term
| Environmental Variation, VE |
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Definition
Variation in a trait among animals in a population caused by non-genetic factors, e.g...
-housing
-feed
-temperature
-disease
-activity
-etc. |
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Term
| The source of variation in a phenotypic value of a trait can be due to... |
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Definition
1: genotypic variation
2: environmental variation |
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Term
| some types of genotypic variation |
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Definition
1: additive genetic variation
2: non-additive genetic variation |
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Term
| types of non-additive genetic variation |
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Definition
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Term
| heritability in the broad sense |
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Definition
| the extent to which an individual’s phenotype is due to its genotype |
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Term
| how to calculate heritability in the broad sense (H2) |
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Definition
| H2 = VG / VP
or
H2 = (VA + VD + VI) / (VA + VD + VI + VE) |
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Term
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Definition
| heritability in the broad sense |
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Term
| heritability in the broad sense reflects the importance of heredity due to... |
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Definition
(1) transmission of alleles from parents
(2) dominance deviations created at all loci during the formation of zygotes
(3) Epistasis deviations created across all loci in the formation of zygotes, in determining phenotypic values |
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Term
| when Dominance and Epistasis deviations are reconstituted |
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Definition
| any time a zygote (an individual) is formed and therefore create noise in determining the direct influence of allele values in determining phenotypic values |
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Term
| heritability in the narrow sense (h2), or just heritability |
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Definition
| the extent to which phenotype is determined by alleles transmitted from parents to offspring |
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Term
| how to calculate heritability in the broad sense (h2) |
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Definition
| h2 = VA / VP
or
h2 = VA / (VA + VD + VI + VE) |
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Term
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Definition
| heritability in the narrow sense |
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Term
| why heritability is important in breeding programs |
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Definition
| because it determines the degree of resemblance between relatives |
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Term
| how to calculate Genotypic variance, VG |
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Definition
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Term
| how to calculate Phenotypic variance, VP |
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Definition
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Term
| An alternative meaning of heritability |
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Definition
| the regression of allelic value on phenotypic value |
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Term
| how to calculate linear regression (bOP) on 1 parent |
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Definition
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Term
| how to calculate heritability (h2) on 1 parent |
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Definition
| h2 = 2 bOP
h2 = bAP = ((Cov(A,P)) / VP) |
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Term
| how to calculate Additive Genetic variance (VA) on 1 parent |
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Definition
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Term
| how to calculate covariance (Cov (O,P)) on 1 parent |
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Definition
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Term
| relationship between heritability (h2), linear regression (bOP), and covariance (Cov (O,P)) |
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Definition
| h2 = 2 bOP = ((Cov(O,P)) / VP) = ((1/2 * VA) / VP)
VA = 2 (Cov, OP) |
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Term
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Definition
| the genetic merit of an animal for a given trait. BV is expressed as a deviation from the mean genetic merit of the trait within a defined population |
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Term
| The genotype of an individual consists of... |
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Definition
(1) allelic values
(2) dominance values
(3) epistastic values |
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Term
| how to calculate an animal's transmitting ability (TA) |
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Definition
TA = 1/2 * EBV
EBV = expected breeding value |
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Term
| how to calculate breeding value (BV) |
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Definition
| BV = h2p
BV = 2 * (P - [P-bar]) |
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Term
| how to calculate expected breeding value (EBV) |
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Definition
| EBV = h2 * (P - [P-bar])
EBV = ((nh2) / (1 + (n - 1)re)) * (P - [P-bar])
EBV = ((ngh2) / (1 + (n - 1)t)) * (P - [P-bar])
g = genetic relationship (1/2 for full siblings and 1/4 for half siblings) |
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Term
| how to calculate accuracy (ACC) of EBV |
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Definition
| Acc = √(h2 * g)
Acc = √((((nh2) / (1 + (n - 1)re))) * g)
Acc = √((((ngh2) / (1 + (n - 1)t))) * g)
g = genetic relationship (1/2 for full siblings and 1/4 for half siblings) |
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Term
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Definition
| a measure of the reliability or strength of the relationship between repeated measurements on an individual |
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Term
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Definition
| bAP = ((Cov(A,P)) / VP)
bAP = (nh2) / (1 + (n - 1)re) |
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Term
| genetic relationship between full siblings (FS) |
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Definition
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Term
| genetic relationship between half siblings (HS) |
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Definition
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Term
| similarity among full siblings (t) |
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Definition
| tFS = (1/2 * h2) + c2FS
c2 = environmental correlation among siblings |
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Term
| similarity among half siblings (t) |
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Definition
| tHS = (1/4 * h2) + c2HS
c2 = environmental correlation among siblings |
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