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28 Cards in this Set
- Front
- Back
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What three people won the Nobel Prize for the genetic analysis of development in Drosophila
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Nusslein-Volhard, Wischaus, Lewis
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Development in Drosophila can be split into the segment of the embryo into ___ segments: ___ head, ___ thorax, __ abdomen
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17 segments: 6 head, 3 thorax, 8 abdomen
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Drosophila ovary consists of what?
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Series of ovarioles
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Ovarioles
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Progression of series of oocytes from initial asymmetric mitotic division of stem cell at tip to growth of final oocyte in vitellarium before going to oviduct where it's fertilized
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Each oogonium undergoes ___ mitotic divisions leading to _______
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4 mitotic divisions, leading to 16-cell germline cyst
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What is the fate of the cells in the germline cyst?
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15 become nurse cells, 1 is the oocyte
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Nurse cells
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Provision the oocyte
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Follicle cells
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Epithelial layer of somatic cells that line the oocyte and contribute additional proteins and signals
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Where are the stem cells in the ovary?
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At the very tip
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Why are nurse cell nuclei darker than the oocyte nucleus?
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They are highly polytenized because they make a large number of proteins
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Ring canals
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Canals from the nurse cell to the oocyte where proteins, etc. are dumped in
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Embryogenesis steps
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Cleavage, form syncitial blastoderm, poll cells form in back as germ line, cellular blastoderm, gastrolation, germ-band extension and retraction for organ dev
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Drosophila cleavage
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Zygote nucleus divides many times without cytokinesis = large syncitial embryo, like morula but with naked nuclei
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Synctitial blastoderm
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Blastula: naked nucleai from cleavage migrate to exterior
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Cellular blastoderm stage
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Overall fate of cells determined, nuclei at posterior pole will become germline, nuclei become cellularized
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How long does it take from egg to first instar larva?
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24 hours
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How long does it take to reach cellular blastoderm and how many cells is it?
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3 hours, 5000 cells
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How is polarity determined in Drosophila?
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Nurse cell end = anterior, anterior-posterior polarity
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Morphogens
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Proteins that are deposited in oocyte by nurce cells and establish anterior-posterior polarity
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Mutations in maternal effect genes cause what?
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Sterility
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How are segmentation genes expressed?
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anterior to posterior
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Maternal effect genes
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Required to be transcribed only in the mother, not the zygote
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Segmentation genes called what
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Kick in with zygotic transcription: gap, pair-rule, and segment polarity genes
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Segmentation genes do what?
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Refine maternal pattern to 14 segments and their anterior-posterior polarity
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Mutations in segmentation genes cause what?
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Embryonic death
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Homeotic genes do what?
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Determine identities of the segments
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Mutations of homeotic genes cause what?
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Dominant transformations of one segment to phenotype of another, usually also dead in homozygotes
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Who were best known for their work on homeotic genes?
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Lewis, Nusslein-Volhard, Wieschaus
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