BIOL 1st Edition Lecture 17 Outline of Last Lecture I History of Genetics II Background of Mendel s Experiments III Mendel s Experiments IV Mendel s Law of Segregation V VI Mendelian Genetics Vocabulary Mendel s Experiments Interpreted Using Modern Terminology Punnett Squares VII Mendel s Law of Independent Assortment VIII Human Genetics Outline of Current Lecture I Intermediate Inheritance II Multiple Alleles III Epistasis IV Polygenic Traits V Pleiotrophy VI Environmental Influence Current Lecture I Intermediate Inheritance a Also known as incomplete dominance b Example cross a red flower plant with white flowered plant i Expect F1 to be all red ii Instead all pink not Mendelian dominant and recessive iii Called blended inheritance II Multiple Alleles a Greater than 2 alleles in population always 2 per individual b Example human blood types i A B O alleles in human population ii A B are co dominant O is recessive iii Possible Genotypes 1 AA or AO phenotype A 2 BB or BO phenotype B 3 AB phenotype AB 4 OO phenotype O III Epistasis a One gene affects expression of another gene b Example sweet peas white variety x different white variety i F1 is all purple because purple flowers require a dominant allele of 2 different genes called P and C ii Both parents were white because they need one dominant alleles for both P and C 1 PPcc first white x ppCC different white iii F1 Purple because all heterozygous PpCc c Occurs through a metabolic pathway i Example A P enzyme B C C enzyme D purple pigment IV Polygenic Traits a One trait determined by more than one gene b Example human height not simple tall or short continuous variation c Example human skin color 3 genes 6 alleles V Pleiotrophy a One gene influences more than one trait b Example albinism and cross eyed phenotype in tigers both caused by one gene c Example sickle cell disorder resistance to malaria determined by same gene VI Environmental Influence a Same genes may not produve same phenotype in different environments b Due to differential expression c Example Identical twins same genotype i One sun tanned ii One not
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