BIOL 1441 1st Edition Lecture 25 Outline of Last Lecture I The Laws of Probability II The Multiplication Rule III Extending Mendelian genetics for a single gene IV The Spectrum of Dominance V Multiple Alleles VI Pleiotropy Outline of Current Lecture I Epistasis II Polygenic inheritance III Multifactorial traits IV Recessively inherited disorders V Inbreeding VI Dominantly inherited disorders VII Multifactorial disorders VIII Appling mendelian genetics to human inheritance IX Dominant recessive inheritance X Pedigree analysis Current Lecture These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute I II III IV V Epistasis 2 different genes a Epistasis gene at one locus alters the phenotypic expression of a different gene at a second locus b Mice coat color depends on two genes i Gene one determines the type of pigment color 1 B for black dominant 2 b for brown recessive ii Gene two determines whether the pigment will be deposited in the hair 1 C for pigment color dominant 2 c for no pigment color recessive Polygenic Inheritance a Quantitative traits vary in the population along a continuum b Usually indicates polygenic inheritance additive effect of two or more genes on a single phenotype i Skin color height are examples of polygenic inheritance Multifactorial Traits a Phenotype is affected by environment as well as genotype b Hydrangea flowers of the same genotype range from blue violet to pink depending on soil acidity c Nutrition influences height d Exercise influences your muscle tone e Sun influences your skin color Recessively Inherited Disorders a Recessively inherited disorders show up only in individuals homozygous for the allele b Carriers heterozygous individuals who carry one recessive allele but are phenotypically normal i Make a sufficient amount of protein c Parents are normal don t know they are carriers of a disease baby gets the disease d Genotypes i AA healthy ii Aa healthy phenotype carrier iii aa disease e Ex Tay Sachs cystic fibrosis sickle cell Inbreeding a Matings between relatives can increase the probability of the appearance of a genetic disease b Rare disease unlikely you will meet another carrier for the disease and marry and have children c If it s a sibling or 1st cousin very high probability that they are a carrier also d Consanguineous matings inbreeding e Popular at one time preserve royal blood VI VII VIII IX X Dominantly Inherited Disorders a More rare in populations lethal most will die before they pass the gene on b Achondroplasia form of dwarfism that is lethal when homozygous for the dominant allele c Genotypes i AA disease ii Aa disease iii aa healthy d What if the disorder doesn t kill you until later i Ex Huntington s Disease 1 Degenerative disease of the nervous system 2 No obvious phenotypic effects until about 35 to 40 yrs of age 3 Once deterioration of the nervous system begins irreversible and fatal Multifactorial Disorders a Many diseases have both genetic and environment components b Little is understood about the genetic contribution to most multifactorial diseases prevention is key c Heart disease cancer diabetes alcoholism schizophrenia bipolar disorder d Exercise diet smoking Applying Mendelian Genetics to Human Inheritance a We produce too few offspring for significant results b Collect family history for a particular trait make a pedigree or family tree Dominant Recessive Inheritance a Dominant trait if you have it one of your parents must express it i Both parents can have a dominant trait and you don t they would be heterozygous 1 Ww Ww ww b Recessive trait if you have it neither parents have to have it heterozygous Pedigree Analysis a Pedigrees used to make predictions about future offspring b We can use the multiplication and addition rules to predict the probability of specific phenotypes c Pedigree characteristics i Male square ii Female circle iii Shaded if you have trait