Lecture 17 Outline of Last Lecture I. History of GeneticsII. Background of Mendel’s ExperimentsIII. Mendel’s ExperimentsIV. Mendel’s Law of SegregationV. Mendelian Genetics VocabularyVI. Mendel’s Experiments Interpreted Using Modern Terminology (Punnett Squares)VII. Mendel’s Law of Independent AssortmentVIII. Human GeneticsOutline of Current Lecture I. Intermediate InheritanceII. Multiple AllelesIII. EpistasisIV. Polygenic TraitsV. PleiotrophyVI. Environmental InfluenceCurrent LectureI. Intermediate Inheritancea. Also known as incomplete dominanceb. Example: cross a red flower plant with white flowered planti. Expect F1 to be all redii. Instead all pink = not Mendelian dominant and recessiveiii. Called “blended inheritance”II. Multiple Allelesa. Greater than 2 alleles in population (always 2 per individual)b. Example: human blood types BIOL 1st Editioni. A, B, O alleles in human populationii. A & B are co-dominant, O is recessiveiii. Possible Genotypes:1. AA or AO phenotype A2. BB or BO phenotype B3. AB phenotype AB4. OO phenotype OIII. Epistasisa. One gene affects expression of another geneb. Example: sweet peas white variety x different white varietyi. F1 is all purple because purple flowers require a dominant allele of 2 different genes called P and Cii. Both parents were white because they need one dominant alleles for both P and C1. PPcc first white x ppCC different whiteiii. F1 Purple because all heterozygous PpCc c. Occurs through a metabolic pathwayi. Example: A P-enzyme B C C-enzyme D (purple pigment)IV. Polygenic Traitsa. One trait determined by more than one geneb. Example: human height not simple tall or short; continuous variationc. Example: human skin color 3 genes/6 allelesV. Pleiotrophya. One gene influences more than one traitb. Example: albinism and cross-eyed phenotype in tigers both caused by one genec. Example: sickle cell disorder/resistance to malaria determined by same geneVI. Environmental Influencea. Same genes may not produve same phenotype in different environmentsb. Due to differential expression c. Example: Identical twins (same genotype)i. One sun-tannedii. One
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