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MITOSIS

MITOSIS. B I N A R Y F I S S I O N. 1. The number of chromosomes varies within species 2. Chromosomes are composed of chromatin a. Complex of 40% DNA and 60% protein b. Contains some RNA since DNA is the site of RNA synthesis DNA exists as a long double-stranded fiber

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MITOSIS

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  1. MITOSIS

  2. BINARY FISSION

  3. 1. The number of chromosomes varies within species 2. Chromosomes are composed of chromatin a. Complex of 40% DNA and 60% protein b. Contains some RNA since DNA is the site of RNA synthesis DNA exists as a long double-stranded fiber DNA coiled to fit into a smaller space than otherwise possible 5. DNA resembles a string of beads 5 a. DNA is coiled around histone polypeptides every 200 nucleotides b. Eight histones form a core called a nucleosome c. Basic, positively charged histones attract negatively charged DNA d. String of nucleosomes further wrapped into supercoils 1. Heterochromatin a. Highly condensed portions of chromatin b. Some portions permanently condensed to prevent DNA expression 2. Euchromatin a. Remainder of chromatin condensed only during cell replication e. DNA is uncondensed to allow for gene expression 6. Chromosomes vary widely in appearance a. Position of the centromere b. Relative length of the arms on either side of the centromere c. Size and staining properties d. Position of additional constricted regions along arms

  4. INTERPHASE S (DNA synthesis) G1 Cytokinesis G2 Mitosis MITOTIC (M) PHASE

  5. M phase: mitosis1. Microtubular apparatus assembled2. Sister chromatids move apart from one another3. Mitosis subdivided into four continuous stages

  6. 1. Interphase a. G1 phase: cells undergo major portion of growth b. S phase:chromosome replicates to produce sister chromatids 1. Remain attached at the centromere 2. Location specific to each chromosome c. G2 phase: chromosomes begin process of condensation 1. Condensation of DNA 2. In G2 cells assemble machinery used to move chromosomes apart a. Animals replicate centriole, nuclear microtubule- organizing centers,mitochondria,ect b. Eukaryotic cells synthesize tubulin, microtubule protein component 3. Restructuring of microtubules and assembly at spindle d. Go phase:

  7. 1. Prophase Individual condensed chromosomes visible- Condensation continues Ribosomal RNA synthesis ceases, nucleolus disappears c. Spindle fibers begins to assemble(microtubules) d. In plant cells, spindle apparatus forms Nuclear envelope breaks down

  8. METAPHASE a. Begins when pairs of sister chromatids align in center of the cell b. Chromosomes align along the metaphase plate c. Centromeres are equidistant from each pole d. Centromeres divide at the end of metaphase e. Centromere splits in two-All centromeres divide in synchrony

  9. ANAPHASE a. Shortest phase, during which sister chromatids separate b. Chromatid drawn to pole to which it is attached • Separation achieved by two simultaneous microtubular actions d. Poles move apart 1. Microtubular spindle fibers slide past one another. Kinetochore 2. Microtubules are anchored at poles which are pushed apart e. Centromeres move toward poles-Shortening not a contraction. Microtubules shorten as tubulin subunits are removed

  10. TELOPHASE • Reform Nuclear membrane-karyokinesis a. Separation of chromatids completes division of replicated genome b. Nuclear envelope re-forms around each new set of chromosomes e. Chromosomes begin to uncoil to allow gene expression f. rRNA genes begin transcription, nucleolus reappears g. Mitosis(Mphase) Complete at End of Telophase h. Replicated genome divided-two new nuclei-opposite ends of cell i. Organelles assort to regions that will become separated

  11. CYTOKINESIS C phase: cytokinesis-Plants and Animals Progresses Differently a. Animal cytokines 1. Cell is pinched in two by a constricting belt of microfilaments 2. Actin filaments slide past one another 3. Produces distinct cleavage furrow around circumference of cell 4. Furrow deepens until the cell is literally pinched in two b. Plant cytokinesis 1. Rigid cell wall, cannot be deformed by microfilament contraction 2. Membrane components assembled in the cell interior 3. Expanding partition called the cell plate 4. Grows outward to the interior surface of the cell membrane 5. Cellulose then added on the membrane making two new cells

  12. GROWTH FACTORS • SIGNALING PATHWAYS--LINK CYCLIN KINASES TO PROCESS. • ANAPHASE SISTER CHROMATIDS STAY T OGETHER UNTIL KINETOCHORES ARE PROPERLY ATTACHED • ANCHORAGE DEPENDANCE • DENSITY DEPENDENT FACTORS-EXTERNAL FACTORS • CELL CROWDING -REACHES POINT WHERE TOUCH-STOP • NOT ENOUGH NUTRIENTS TO TAKE CARE OF MORE • FACTOR PLATELET-DERIVED GROWTH FACTOR • DERIVED FROM PLATELETS • BIND TO PDGF RECEPTORS ON MEMBRANE • TRIGGER THRU SIGNAL TRANSDUCTION PATHWAY TO STIMULATE CELL TO PASS G1 CHECKPOINT AND DIVIDE.

  13. FACTOR PLATELET-DERIVED GROWTH

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