Multifactorial Traits
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Transcript Multifactorial Traits
Multifactorial Traits
Nomenclature
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
Continuously varying
Called a quantitative
trait
Genes are called
quantitative trait ____
_________ is a bell
curve
Locus Models
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
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
Genetics contribute ________ attainable height
Environment determines height actually attained
Eye Color
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
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
Genetics
Amount of cholesterol
Blood pressure
Clotting factors
Environment
Diet
Exercise
Weight
Very complex genetically
Feeling of hunger
Metabolism
Environment
Diet
Exercise
Empiric Risk
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
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
_____________ (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?
Adoption Studies
Adoptee is compared to adopted parents
(environment)
Adoptee is compared to biological parents (genetics)
Twin Studies
Prevalence of trait between MZ twins is compared to
DZ twins (concordance)
Higher differences in concordance show higher
differences in heritability
Association Studies
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