Multifactorial Traits
Nomenclature
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Mendelian trait- trait caused by alleles on
______________
____________ trait- trait caused by more
than one gene often on different
chromosomes
Multifactorial (complex) trait- trait that has
_______________________ components
Genetics vs Environment
Polygenic Phenotypes
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Continuously varying
Called a quantitative
trait
Genes are called
quantitative trait ____
_________ is a bell
curve
Locus Models
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Model is based on how many loci code for
each polygenic trait
As the number of genes increase, so does
the amount of phenotypes possible
Number of _______________ determines
phenotype
Fingerprint Patterns
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Dermal ridges form
patterns of loops, whorls,
or arches
Mostly determined by
___________
Influenced by touching
fingers and toes to
amniotic sac during early
development
Total ridge count (TRC)count of ridges on all
fingerprints; creates bell
curve
Height
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Genetics contribute ________ attainable height
Environment determines height actually attained
Eye Color
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Probably ______, but not
multifactorial
True blue eyes- no active
pigment; blue color comes
from scattering of light
Lipochromes- greenish-blue pigment
Melanins- brownish pigment
Melanins tend to mask other
pigments
Other features (flecks, specks, rings,
and streaks) come from distribution
of pigment on the iris
Skin Color
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Color created by bits
of melanin secreted
by melanocytes within
the layers of the skin
Variety created by
genes coding for
amount and
distribution of
melanin
Cardiovascular System
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Genetics
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Amount of cholesterol
Blood pressure
Clotting factors
Environment
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Diet
Exercise
Weight
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Very complex genetically
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Feeling of hunger
Metabolism
Environment
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Diet
Exercise
Empiric Risk
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Rate at which a certain trait occurs within
a _______________
Population may be defined vaguely or very
specifically
Risk may increase within certain ethnic
groups or if family members are affected
Heritability
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Expresses proportion of phenotype that is
contributed to __________ for a particular
trait
1.0 would be solely based on genetics
Lower number have ________________
components
Number can change when environment
changes
Coefficient of Relatedness
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_____________ (P)- individual based
relatedness is based upon
1°- Immediate family members (mother, father,
sister, brother, children); share _____ of genes
2°- Grandparents, aunts, uncle, nieces, and
nephews, grandchildren; share _____ of genes
3°- Great grandparents, great aunts, great
uncles, great nieces, great nephews, first
cousins, great grandchildren; share ______ of
genes
How do we study nature vs
nurture?
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Adoption Studies
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Adoptee is compared to adopted parents
(environment)
Adoptee is compared to biological parents (genetics)
Twin Studies
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Prevalence of trait between MZ twins is compared to
DZ twins (concordance)
Higher differences in concordance show higher
differences in heritability
Association Studies
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Researchers compare SNP’s (single nuclear
polymorphisms) between individual with and
without disorders
Groups with disorder may show a characteristic
set of SNP’s
Can be used to find genes that are causing
disorder
Can be difficult because of genetic heterogeneity