BIOL-L 211 Lecture 3 Outline of Last Lecture I. PangenesisII. LamarckismIII. Blending Theory of InheritanceIV. Arrival of Gregor MendelOutline of Current Lecture I. Drosophila MelanogasterA. Model OrganismsB. Drosophila in ResearchC. Important ResearchersD. Discovery of Sex-Linked TraitsII. Crossing OverA. Proximity FactorB. Crossing OverIII. Additional PointsA. Incomplete DominanceB. Co-dominanceCurrent LectureDrosophila As a Model SystemI. Drosophila Melanogaster (common fruit fly)A. Drosophila Melanogaster is what is known as a model organism1. A model organism is a non-human, widely studied organism with a genome that is easily sequenced and similar to humans2. Common model organisms: drosophila melanogaster, yeast, E. Coli, and arabidopsis thalianaThese 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.B. Drosophila Melanogaster in research1. Has only 4 chromosomes, which facilitates gene manipulation2. Life cycle of only 10 days (speeds up research) – results obtained quickly3. Flies are compared to the "wild type," which is the normal typeC. Important People in Research of the Drosophila Melanogaster1. William Ernst Castle (1906): First to use flies2. Thomas Hunt Morgan (1933): Nobel Prize for his research in the field of genetics- specifically with individual chromosomes3. Herman Muller (1946): IU Professor!! Demonstrated that x-rays cause mutations (which is good to know)4. Dr. Kaufman (2014): Discovered 1,468 new genes (in the drosophila melanogaster genome) post the genome being sequencedD. Discovery of Sex-Linked traits via Drosophila Melanogaster1. Examined progeny of mutant male with white eyes2. Found that eye color was only transmitted with X-chromosome3. With only one X-chromosome present (in males), the x-linked gene could be expressed!II. Crossing OverA. Proximity factor1. Thomas Hunt Morgan (mentioned earlier) noted that some allele combos inherited more frequently than others2. Andrew Sturtevant (another researcher) proposed that perhaps proximity played a factor3. Proximity: the distance between a set of genes on a chromosomeB. Crossing over1. Type of recombination (rearrangement of genes) that occurs in Prophase I and NOT in Mitosisa. This is very important to noteb. The cell cycle is discussed in detail in a later lecture2. Exchange of material between non-sister chromatids of homologous chromosomesa. Quick reminder: homologous chromosomes: the set of one chromosome from each parent cell that code for similar traitsb. Non-sister chromatids: chromatids that aren't already linked together3. Barbara McClintock (1900s) & Harriet Creighton's Discoveriesa. Found that crossing over involved physical exchange of genetic informationb. Research involved different types of cornc. Research was not recognized for fifty years because they were womend. Also discovered transposons (to be discussed in a later lecture)4. Do NOT need to be able to sequence genesIII. Additional PointsA. Incomplete Dominance: replaced blending theory- explained how an organism could display an apparent blend of parental traitsB. Co-dominance: Explained how an organism could exhibit two traits equally[ex: blood
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