Download h 2

Quantitative Genetics
*discontinuous variation
*continuous variation
*Multiple-factor hypothesis
*Kolreuter – continuous phenotypic
variation in tobacco plants
Additive Alleles
Intermediate
More variation
Variation, but
similar to F2
Quantitative Genetics
Polygenic Inheritance
*Statistical Analysis
Normal frequency distribution:
*Mean
*Variance
*Standard Deviation
*Standard Error
Variance:
Polygenic Inheritance
*Complex traits
*multifactorial
Glazier, A. et al. 2002. Finding Genes
That Underlie Complex Traits. Science,
298, p.2345-2349
Nature vs. Nurture: The Genetics View
*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
*Genetic control
*Heritability
Estimates of Heritability for Traits in
Different Organisms
Trait
H2 = VG
Heritability (% h2)
Mice
VP
Tail Length
60
Body Weight
37
But, P = G + E
Litter Size
15
Chickens
h2 =
VG
V P + VE
Body Weight
50
Egg Production
20
Egg Hatchability
15
Cattle
Birthweight
51
Milk Yield
44
Conception Rate
3
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