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biol139-lecture14-2011 - Next topic Next Mitosis Mitosis...

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Unformatted text preview: Next topic Next Mitosis Mitosis Chapter 4 con’t Chapter pp 88 - 92 pp pp 42 - 46 iGenetics The eukaryotic cell The • bounded by a plasma membrane plasma The nucleus n Nucleus contains DNA (genetic material) complexed with proteins. Nucleus DNA Organized into chromosomes (chromatin) chromosomes Nucleus separated from rest of cell by double membrane nuclear membrane nuclear Chromatin – the complex of DNA and protein found in a cell’s nucleus nucleus - Repeating pattern of growth, mitosis and cell division is called the cell cycle Majority of cycle is Interphase 2N 2N GAP 2 Cell prepares for mitosis makes essential proteins Mitosis: division of 1 complete set of chromosomes to each progeny nuclei start GAP 1 Synthesis phase • Duplicates DNA (chromosomes) • Identical sister chromatids • joined at centromere • prepare for DNA replication • gets large enough to divide • most of time spent in this phase (depends on cell type) • actively producing many products specific to biological role in body Mitosis Mitosis The process of nuclear division in cells that produces daughter cells that are genetically identical to each other and to the parent cell Series of 5 distinct phases Prior to Prophase (Interphase) Prior • microtubules become visible • radiate from a structure called a Centrosome • each centrosome has a pair of centrioles in center • centrosome replicates during interphase • producing 2 centrosomes (close proximity) • nuclear membrane still intact • in interphase DNA is mass of chromatin in nucleus Centrioles Microtubules 1 Centrosome cytoplasm Nuclear membrane Chromatin, DNA, chromosomes nucleolus nucleus Centrosome – microtubule Centrosome organizing center, the core of which is seen as two of darkly staining bodies in animal cells, known as animal centrioles Prophase Prophase 2n = 4 . replicated chromosomes begin to condense and become visible . nucleolus disappears . centrosomes begin to move apart toward opposite poles . generation of new microtubules (radiate out) • nuclear membrane still intact nuclear Prometaphase Prometaphase 2n = 4 Kinetochore – site at which chromosome is Kinetochore attached to microtubules .degradation of nuclear membrane .nucleolus gone .microtubules invade the nuclear area (3 types) .each sister chromatid attaches to microtubules from opposite centrosome at the kinetochore kinetochore Kinetochore = Site at which Chromosome is attached to microtubule Prophase ends when kinetochore of each sister chromatid is each attached to microtubule from centromere of opposite pole Mitotic Spindle: originate from centrosomes at “poles” Mitotic Short, unstable Radiate from centrosome to periphery Microtubules which attach to kinetochore Polar Microtubules: directed to middle of cell Do not attached to kinetochore Electron Micrograph showing the association between microtubules constituting the spindle fibers and the kinetochore (in association with a centromere) during mitosis Metaphase Metaphase 2n = 4 Each chromosome pair aligns on the metaphase plate • chromosomes align center of cell between poles at 900 angle • line up on imaginary plate called metaphase plate • sister chromatids facing opposite poles Anaphase Anaphase 2n = 4 .sister chromatids separate at centromere .separated sister chromatids move to opposite poles by action of microtubules (at kinetochore) action = called disjunction disjunction Telophase Telophase .nuclear membrane and nucleoli reform .spindle fibers disappear .chromosomes uncoil and become a tangle of chromatin Cell division = cytokinesis -division of the cytoplasm • cell divides with 2 nuclei cell • • • • cytoplasm divides cytoplasm begins anaphase and completed after telophase begins pinched in by contractile ring contractile two daughter cells with identical nuclei identical Cytokinesis Cytokinesis Animal cells Plant cells The cytoplasm divides, splitting the parent The cell into two daughter cells with identical nuclei cell ...
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