Quantitative Genetics *discontinuous variation *continuous variation *Kolreuter – continuous...
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Transcript of Quantitative Genetics *discontinuous variation *continuous variation *Kolreuter – continuous...
Quantitative Genetics*discontinuous variation*continuous variation
*Kolreuter – continuous phenotypic variation in tobacco plants
*Multiple-factor hypothesis
Additive Alleles
Intermediate
More variation Variation, but similar to F2
Quantitative Genetics
Polygenic Inheritance
*Statistical Analysis
Normal frequency distribution: Variance:
*Mean
*Variance
*Standard Deviation
*Standard Error
Polygenic Inheritance
*Complex traits*multifactorial
Glazier, A. et al. 2002. Finding Genes That Underlie Complex Traits. Science, 298, p.2345-2349
*Phenotype depends on environment and genes
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
Nature vs. Nurture: The Genetics View
Nature vs. Nurture: The Genetics View
*Genetic control
*Heritability
H2 = VG
VP
h2 = VG
VP + VE
But, P = G + E
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
Estimates of Heritability for Traits in Different Organisms
Nature vs. Nurture: The Genetics View
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
Comparison of Concordance of Various Traits Between
Monozygotic (MZ) and Dizygotic (DZ) Twins