320Fall09Lecture21 - BIO 320 Cell Biology, Fall 09 Dr....

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BIO 320 Cell Biology, Fall ‘09 Dr. Thomas Bushart Lecture 21
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Topics Apoptosis Cell adhesions - cadherins
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Diseases and uses Problems with meiosis can generate gametes with inappropriate chromosome numbers I Most are not viable I Down syndrom – trisomy of chromosome 21 I Turner’s – single X I Klienfelter’s syndrome (XXY) and XXX and XYY compliments tend to have normal lifespans May be slight physical or behavioral manifestations Any XYY connection to crime and/or violence is unlikely to be a direct one Cancer treatments Fruit crops often are tetraploids (or higher)
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Fruit crops Colchicine can inhibit mitosis I Binds to tubulin, inhibiting MT growth I S phase without mitosis doubles chromosome number I Inhibition of meiosis while still allowing cytokinesis produces 2n gametes Tetraploid (4n) plants may be larger and heartier I Even number polyploids may restore fertility to odd hybrids Triploid plants (4n X 2n cross = 3n) can be seedless (watermelons, bananas)
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Bananas
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Programmed cell death Apoptosis (a type of PCD) I Apo + ptosis (falling away from), in Greek “p” is silent in “pt” I Helix + pteron = helicopter (“helicoter?”) The orderly breakdown and death of a cell I Cell surface alters to signal uptake by professional phagocytes (orderly clean up)
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PCD vs necrosis Necrotic cells leak contents I May induce inflammatory responses
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Roles for PCD/apoptosis Elimination of unwanted cells during development I Hand/paw sculpting, tadpole tails I Adjustments to the nervous system “Quality control” – damaged or abnormal cells Organ size maintenance with cell turnover
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Molecular changes DNA fragments I Forms distinctive ladders due to nucleosomes Plasma membrane changes I Phosphatidylserine ends up in outer leaflet “Eat me” signal Inhibits inflammatory response of phagocyte I Loss of “don’t eat me” signals Mitochondria I Loss of electrical potential I Freed cytochrome C
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This note was uploaded on 01/25/2010 for the course BIO 51055 taught by Professor Bushart during the Fall '09 term at University of Texas at Austin.

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320Fall09Lecture21 - BIO 320 Cell Biology, Fall 09 Dr....

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