Bios 208 1st Edition Lecture 30 Outline of Last Lecture I. Behavior of Chromosome Sets in the Human Life CycleII. The Variety of Sexual Life CyclesIII. The Stages of MeiosisIV. A Comparison of Mitosis and MeiosisV. Sources of Variation in sexual life cyclesOutline of Current Lecture I. Gregor MendelII. A Genetic CrossIII. Genotype versus phenotypeIV. Useful Genetic VocabularyCurrent LectureI. Gregor MendelA. Agrarian upbringingB. Studied math, chemistry and physics inC. Vienna – mathematical descriptions of nature D. Augustinian monk in Brnö. Teacher; later became abbot.E. Pea breeding experiments, ca. 1855-1865.F. Published results in 1866. Sent papers to European scientists … no response!G. His notes were burned after he died.H. Discoveries: mitosis, 1875; meiosis, 1890I. Results and laws rediscovered in 1900 (Correns, Tschermak, DeVries).II. A Genetic CrossA. Crossing pea plants Self-cross:B. Peas are self-fertile.C. Pollen (which carries sperm) can fertilize carpels (which contain eggs) from the same flowerD. True-breeding plants produce one kind of offspring (purple or white)E. Out-cross or hybridization: transfer of pollen to another plantF. Seeds are the offspring. They grow into plants with the same genes.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.G. Parents: Cross true-breeding purple and white parentsH. F1 generation: all offspring have purple flowersI. F2 generation: mostly purple, some whiteJ. Mendel counted: 705 purple,K. 224 white, ~ 3:1 ratioL. Every gene occurs on a specific chromosome and a specific location or locus (pl. loci).M. Alleles are alternative forms of a gene.III. Genotype versus phenotypeA. Each parent carries 2 factors for each trait, PP or pp (we call factors genes)B. Gametes (eggs and sperm) contain one copy of each factor (P or p).C. Offspring get one factor from each parent. In the F1 (Pp), the recessive factor is present but masked by the dominant factor.D. F1 plants make gametes containing either P or p. Fertilization produces zygotes (F2 generation) that are PP, Pp or ppIV. Useful Genetic VocabularyA. An organism with two identical alleles for a character is said to be homozygous for the gene controlling that characterB. An organism that has two different alleles for a gene is said to be heterozygous for the gene controlling that characterC. Unlike homozygotes, heterozygotes are not true-breedingD. Because of the different effects of dominant and recessive alleles, an organism’s traits donot always reveal its genetic compositionE. Therefore, we distinguish between an organism’s phenotype, or physical appearance, and its genotype, or genetic makeupF. In the example of flower color in pea plants,G. PP and Pp plants have the same phenotype (purple) but different
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