Multifactorial Traits

Nomenclature Mendelian trait- trait caused by alleles on ______________ Mendelian trait- trait caused by alleles on ______________ ____________ trait- trait caused by more than one gene often on different chromosomes ____________ trait- trait caused by more than one gene often on different chromosomes Multifactorial (complex) trait- trait that has _______________________ components Multifactorial (complex) trait- trait that has _______________________ components

Genetics vs Environment

Polygenic Phenotypes Continuously varying Continuously varying Called a quantitative trait Called a quantitative trait Genes are called quantitative trait ____ Genes are called quantitative trait ____ _________ is a bell curve _________ is a bell curve

Locus Models Model is based on how many loci code for each polygenic trait 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 As the number of genes increase, so does the amount of phenotypes possible Number of _______________ determines phenotype Number of _______________ determines phenotype

Fingerprint Patterns Dermal ridges form patterns of loops, whorls, or arches Dermal ridges form patterns of loops, whorls, or arches Mostly determined by ___________ Mostly determined by ___________ Influenced by touching fingers and toes to amniotic sac during early development 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 Total ridge count (TRC)- count of ridges on all fingerprints; creates bell curve

Height Genetics contribute ________ attainable height Genetics contribute ________ attainable height Environment determines height actually attained Environment determines height actually attained

Eye Color Eye Color Probably ______, but not multifactorial Probably ______, but not multifactorial True blue eyes- no active pigment; blue color comes from scattering of light True blue eyes- no active pigment; blue color comes from scattering of light Lipochromes- greenish-blue pigment Lipochromes- greenish-blue pigment Melanins- brownish pigment Melanins- brownish pigment Melanins tend to mask other pigments Melanins tend to mask other pigments Other features (flecks, specks, rings, and streaks) come from distribution of pigment on the iris 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 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 Variety created by genes coding for amount and distribution of melanin

Cardiovascular System Genetics Genetics Amount of cholesterol Amount of cholesterol Blood pressure Blood pressure Clotting factors Clotting factors Environment Environment Diet Diet Exercise Exercise

Weight Very complex genetically Very complex genetically Feeling of hunger Feeling of hunger Metabolism Metabolism Environment Environment Diet Diet Exercise Exercise

Empiric Risk Rate at which a certain trait occurs within a _______________ Rate at which a certain trait occurs within a _______________ Population may be defined vaguely or very specifically Population may be defined vaguely or very specifically Risk may increase within certain ethnic groups or if family members are affected 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 Expresses proportion of phenotype that is contributed to __________ for a particular trait 1.0 would be solely based on genetics 1.0 would be solely based on genetics Lower number have ________________ components Lower number have ________________ components Number can change when environment changes Number can change when environment changes

Coefficient of Relatedness _____________ (P)- individual based relatedness is based upon _____________ (P)- individual based relatedness is based upon 1°- Immediate family members (mother, father, sister, brother, children); share _____ of genes 1°- Immediate family members (mother, father, sister, brother, children); share _____ of genes 2°- Grandparents, aunts, uncle, nieces, and nephews, grandchildren; 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 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 Adoption Studies Adoptee is compared to adopted parents (environment) Adoptee is compared to adopted parents (environment) Adoptee is compared to biological parents (genetics) Adoptee is compared to biological parents (genetics) Twin Studies Twin Studies Prevalence of trait between MZ twins is compared to DZ twins (concordance) Prevalence of trait between MZ twins is compared to DZ twins (concordance) Higher differences in concordance show higher differences in heritability Higher differences in concordance show higher differences in heritability

Association Studies Researchers compare SNP’s (single nuclear polymorphisms) between individual with and without disorders Researchers compare SNP’s (single nuclear polymorphisms) between individual with and without disorders Groups with disorder may show a characteristic set of SNP’s Groups with disorder may show a characteristic set of SNP’s Can be used to find genes that are causing disorder Can be used to find genes that are causing disorder Can be difficult because of genetic heterogeneity Can be difficult because of genetic heterogeneity