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Cell Cycle

Why Do We Need It?. What Is It?. Cell Cycle. Interphase. Cellular Structures Glossary. Mitosis. Mitosis Animation. Cytokinesis. The Cell Cycle .

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Cell Cycle

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  1. Why Do We Need It? What Is It? Cell Cycle Interphase Cellular Structures Glossary Mitosis Mitosis Animation Cytokinesis

  2. The Cell Cycle The cell cycle is the sequence of growth and division of a cell. It consists of three major phases: Interphase, mitosis, and cytokinesis. Cell division results in two cells that are both identical to the parent cell.

  3. Why do cells grow and divide? All cells come from other cells. As organisms grow and change (a growing vine, or a tadpole changing to a frog) new cells need to be produced. Cell growth and division also allows worn-out tissues to be repaired and/or replaced.

  4. Mitosis Animation Mitosis

  5. Interphase Interphase is the phase where the cell spends the majority of its life. During interphase, the cell grows, carries on metabolism, and chromosomes are duplicated to form sister chromatids in order to prepare for cellular division.

  6. Mitosis Mitosis is the phase where nuclear division takes place and the cell divides. Mitosis occurs in a sequence of 4 stages: Prophase, metaphase, anaphase, and telophase. View Animation

  7. Cytokinesis Cytokinesis is the final phase of the cell cycle. This is where the cytoplasm divides. In animals, the plasma membrane pinches along the equator of the cell. In plants, the cell plate is laid down across the equator and new cell walls form on each side.

  8. Prophase Prophase is the longest of the mitotic stages. During prophase, four major cellular changes take place: • Chromatin coils to form visible chromosomes. • The nucleus begins to disappear. • Centrioles migrate to opposite ends of the cell. • Spindle fibers begin to form. Mitosis

  9. Metaphase Metaphase is a shorter mitotic stage. Several things occur during metaphase… Mitosis

  10. Metaphase… First, chromosomes begin to move to the equator of the spindle. Mitosis

  11. Metaphase… Each sister chromatid attaches to a separate spindle fiber via its centromere. Mitosis

  12. Metaphase… These spindle fibers extend from opposite poles. This ensures that each new cell receives an identical and complete set of chromosomes. Mitosis

  13. Metaphase… When metaphase is complete, the spindle has formed completely and the sister chromatids are attached along the equator of the spindle. Mitosis

  14. Anaphase During anaphase, the centromeres split, and sister chromatids migrate to opposite poles of the cell. Mitosis

  15. Telophase Telophase is the final stage of mitosis. The chromotids have now reached the poles of the cell and unwind into chromosomes. This allows metabolic activity to recommence. Mitosis

  16. Telophase… Many of the processes that occurred during prophase reverse themselves. Mitosis

  17. Telophase… • The spindle fibers break down • The nucleolus reappears • The nuclear envelope forms • Two nuclei now exist that are identical to the nucleus of the parent cell. Mitosis

  18. Glossary • centriole • centromere • chromatid • chromatin • chromosome • nuclear envelope • nucleolus • nucleus • spindle • spindle fiber

  19. centriole A centriole is a barrel microtuble structure found in most animals cells. Two centrioles arrange themselves perpendicularly to form a centrosome. Centrioles organize the mitotic spindle upon which chromosomes are pulled apart during cellular division. Glossary

  20. centromere The centromere is a region of the chromosome where the spindle fibers of the mitotic spindle attach. The centromere is also the point of attachment of the two sister chromatids once a chromosome has been duplicated for cellular division. Glossary

  21. chromatid A chromatid is one strand of the chromosome after it has duplicated for cellular division. The two chromatids are called “sister chromatids” and will eventually split and move to opposite ends of the cell.

  22. chromatin Chromatin is the building block for a chromosome. It is only made visible by staining. It consists of DNA and proteins. When the cell prepares to divide, the chromatin thickens and can be seen as distinct chromosomes.

  23. chromosome A chromosome is a long, continuous piece of DNA which contains the genetic information for a cell.

  24. nuclear envelope The nuclear envelope is the double membrane of the nucleus in eukaryotic cells. It separates the contents of the nucleus from the cytosol.

  25. nucleolus The nucleoulus is a “suborganelle” of the nucleus. It refers to a “knot” of chromatin located within the nucleus. No membrane surrounds the nucleolus.

  26. nucleus A nucleus is found in all eukaryotic cells. It is a structure that contains the cell’s genetic material. The nucleus controls chemical reactions that take place in the cytosol, regulates expression of genes, and stores information needed for cellular division. The nucleus is surrounded by a membrane called the nuclear envelope.

  27. spindle The mitotic spindle is a network of microtubules that is formed during the prophase stage of mitosis.

  28. spindle fiber A spindle fiber is one of the microtubules comprising the mitotic spindle. Some of these spindle fibers attach to the centromeres of the chromosomes and help draw the chromatids apart during anaphase.

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