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7 Cards in this Set
- Front
- Back
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Explain what is meant by a quantitative trait. Give some examples of quantitative traits.
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–Affected by multiple genes: polygenic inheritance, quantitative trait loci (QTLs)
–Effect of environment is often large –Often have a continuous distribution –Example: human height –Often traits that we are most interested in for conservation |
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phenotypic variation :
VP= VE+ VA+ VD+ VI. What does each variable mean? |
VP= VE+ VG
VP = Phenotype VE = environment VA= additive effects (effects of gene substitution e.g. AA = red flowers, Aa= pink flowers, aa= white flowers) VD= dominance effects (effects of interactions between alleles e.g. BB = brown eyes, Bb = brown eyes, bb = blue eyes) VI= epistatic effects (effects of interactions between loci e.g. mice with genotype aa are albino because all pigment production is blocked, regardless of the phenotype at a second colour locus) |
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How might you experimentally differentiate between environmental and genetic contributions for a quantitative trait?
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breeding experiments and pedigree analyses Eliminate/reduce the environmental or genetic variance
VP= VE+ VG So if VG= 0 then VP= VE or VE= 0 then VP= VG •e.g. studies with twins |
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heritability
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a measure of the influence of genetic factors in determining phenotypic differences among individuals for a trait within a population
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What type of genetic variation is usually used when calculating heritability
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Usually focus on VA, which provides a measure of genetic resemblance between parents and offspring and therefore the predicted response of a trait to selection i.e. it’s a measure of how well quantitative traits are transmitted from one generation to the next
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What does a heritability of zero mean?
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H = 0 is found in highly inbred pops with no genetic variation
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What does a heritability of one mean?
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H = 1, a characteristic is determined purely by genetics with no environmental influence
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