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Mitosis

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Published in: Biology
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The presentation describes the process of mitosis and its various stages.

Monika S / Delhi

3 years of teaching experience

Qualification: M.Sc.(Biotechnology)

Teaches: Bio Technology, Biology, Zoology, Chemistry, Bio-medical, Microbiology

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  1. Cell Cycle and Mitosis
  2. Cell Cycle The cell cycle teo is the life cycle of a cell anaphase etaQYmase (groMh) (synthesis) (preparation)
  3. Interphase Longest stage of cell division (90% of cell cycle) Nucleus is visible 3 sub-phases: Gl: Cell growth S: DNA is copied (DNA Replication) Gin Organelles copied/duplicated to prepare for division. (growth) s (synthesis) 2 (preparation) 4
  4. How is DNA packaged t 2 nm into chromosomes? 11 nm 30 nm 300 nm 700 Centromete 1.400 nm DNA coils around set of 4 histone proteins, creating a "bead on a string" called a nucleosome The nucleosome coils into structures called chromatin Chromatin supercoils = chromosome!
  5. Key vocabulary DNA molecules are packaged into chromosomes — Human somatic cells (body cells) have 46 chromosomes. — Human gametes (sperm or eggs) have 23 chromosomes. Chromosomes are made of a material called chromatin 0.5 pm
  6. Key vocabulary Chromatin is composed of proteins and DNA It is supercoiled around proteins, called histones Together the DNA and histone molecules form bead-like structures called nucleosome
  7. Key vocabulary The chromosome is Chromosome duplication duplicated (during S) Each duplicated chromosome consists Centromere of two sister chromatids These are connected by a centromere Separation of sister chromatids Distribution of new chromosomes to daughter cells Sister chromatids Copyright Pearson Education, Inc., publishing as Benjamin Cummings. 0.5 pm
  8. ate nterp ase: G Preparing for Division (G 2 Of interphase) Centrosomes (with centriole pairs) Nuclear membrane still visible Nucleolus Chromatin has been replicated
  9. Mitosis (M Phase) The M Phase consists of: Mitosis and Cytokinesis Mitosis: the division of the nucleus Cytokinesis: the division of the cytoplasm Four Stages of Mitosis: Prophase Metaphase ' Anaphase Telophase
  10. INTERPHASE microtubules cytosol plasma membrane Prophase I PROPHASE duplicated centrosome nuclear envelope decondensed chromosomes in nucleus intact nuclear envelope kinetochore centrosome Forming mitotic spindle Condensing chromosome Onset of chromosome condensation Intracellular membrane networks are disassembled •Cells begin to round up •Protein synthesis stops •Duplicated centrosomes separate Centrosomes forming mitotic spindles
  11. Prophase In prophase, the cell begins the process of division. 1. The chromosomes condense. The proteins attached to the DNA cause the chromosomes to go from long thin structures to short fat one, which makes them easier to pull apart. 2. The nuclear envelope disappears. The double membrane that surround the nucleus dissolves into a collection of small vesicles, freeing the chromosomes to use the whole cell for division 3. The centrosomes move to opposite poles. During interphase, the pair of centrosomes were together just outside the nucleus. In prophase they separate and move to opposite ends of the cell. 4. The spindle starts to form, growing out of the centrosomes towards the chromosomes.
  12. Metaphase Metaphase is a short resting period where the chromosomes are lined up on the equator of the cell, with the centrosomes at opposite ends and the spindle fibers attached to the Kinetochore. Everything is aligned for the rest of the division process to occur.
  13. Stmcture of the kinetochore m•rQu Imer layer oflåetochore to repeffve centomeric DNA. Outer layer of lüetochore binds to the (+) end of MTS- This Tea is etriched in motor proteins (dynein: MCAK: CENP-E)- Czpyi$.t S 100 i DI All fight:
  14. Capture of chromosomes by kinetochore MTS re it'd pole Copyright S DI All fight: • Occurs via a 'search' and 'capture' mechanism • Microtubules extend fram centrasamestawards chromosomes. • Initial binding afa MT to a chromosomeaccurslaterally. • MT becomes stable andthe binding converts to end-an at kinetachare. • Process is repeated an appasitesideafkinetachare andchramasamesbecame stabilized between kinetachare microtubules.
  15. Anaphase Spindles pull the "daughter" chromosomes appart
  16. Anaphase In anaphase, the centromeres divide. At this point, each individual chromosome goes from: 1 chromosome with 2 chromatids — to: 2 chromosomes with one chromatid each. Then the spindle fibers contract, and the chromosomes are pulled to opposite poles, towards the centrosomes.
  17. Forces that separate daughter chromosomes at anaphase ANAPHASE A shortening 01 kinetochore microtubules; rn"vement of daughter chromosomes to poles; forces generated mainty at kinetochores Figure part of X of the Cell 4 Capyfight S DI All fight: ANAPHA* sliding force from opposite poles to directly 901es to them plus end polar microtubules
  18. How do sister chromatids separate at metaphase/anaphase transition? The multi-protein cohesin complex consists of SMC (st-uctual mahltenance of chromosome) protems • Smc1,Smc3, Sccl and additional proteins form links betneen sister chrornaöds. • Once all kinetochorsare succsåullycapturai(checkpoint l), APC-Cdc20is activatd. • APC-Cdc20 ma rks searin for by polyubiquitination. • Degradationofsecufinenablesseparase(a protease) to beconkactve • Separasecleaves Sccl, pernittingsister chromatidsto separateundertersion from the kinetochore microtubules Copyright S 2005 DI All fight:
  19. Telophase Two nuclei become visible In animal cells, a Cleavage Furrow is visible In plant cells, a cell plate is now visible Cytokinesis The cytoplasm and organelles divide. 25 gm Telophase & Cytokinesis 'l
  20. Telophase In telophase the cell actually divides. The chromosomes are at the poles of the spindle. The spindle disintegrates The nuclear envelope re- forms around the two sets of chromosomes. The cytoplasm is divided into 2 separate cells, the process of cytokinesis.
  21. Nucleus of Wall of Vesicles Nucleus of daughter cell parent cell forming daughter cell jCleavage furrow 100 pm Cleavage furrow Contracting ring of microfilaments Daughter cells (a)Cleavage of an animal cell Copyright Pearson Education, Inc., publishing as Benjamin Cummings. Cell wall Vesicles containing cell plate New cell wall 00-00 Cell plate Daughter cells cell wall material (b) Cell plate formation in a plant cell
  22. How many stages of cell division do you see in this image?
  23. Summary of Mitosis Prophase: Chromosomes condense Nuclear envelope disappears centrosomes move to opposite sides of the cell Spindle forms and attaches to centromeres on the chromosomes Metaphase Chromosomes lined up on equator of spindle centrosomes at opposite ends of cell Anaphase Centromeres divide: each 2-chromatid chromosome becomes two 1 -chromatid chromosomes Chromosomes pulled to opposite poles by the spindle Telophase Chromosomes de-condense Nuclear envelope reappears Cytokinesis: the cytoplasm is divided into 2 cells

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