Quantitative Genetics

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Quantitative Genetics
Kolreuter continuous phenotypic variation in
tobacco plants
discontinuous variation
continuous variation
Multiple-factor hypothesis
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Additive Alleles
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Quantitative Genetics
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Polygenic Inheritance
Statistical Analysis
Variance
Mean Variance Standard Deviation Standard
Error
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Polygenic Inheritance
Glazier, A. et al. 2002. Finding Genes That
Underlie Complex Traits. Science, 298, p.2345-2349
Complex traits
multifactorial
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Nature vs. Nurture The Genetics View
Phenotype depends on environment and genes
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Nature vs. Nurture The Genetics View

• The expression of some genes is influenced by
  environmental factors, such as temperature

• Some alleles are heat-sensitive
• Arctic foxes make fur pigment only when the
  weather is warm

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Nature vs. Nurture The Genetics View
Genetic control Heritability
Estimates of Heritability for Traits in Different
Organisms
Trait Heritability ( h2)
Mice
Tail Length 60
Body Weight 37
Litter Size 15
Chickens
Body Weight 50
Egg Production 20
Egg Hatchability 15
Cattle
Birthweight 51
Milk Yield 44
Conception Rate 3
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Nature vs. Nurture The Genetics View
Comparison of Concordance of Various Traits
Between Monozygotic (MZ) and Dizygotic (DZ) Twins
Trait MZ DZ
Blood Types 100 66
Eye Color 99 28
Mental Retardation 97 37
Hair Color 89 22
Handedness 79 77
Epilepsy 72 15
Schizophrenia 69 10
Diabetes 65 18
Identical Allergy 59 5
Cleft Lip 42 5
Clubfoot 32 3