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Understanding Mitosis: The Process of Cell Division and Growth

This comprehensive guide explores the intricacies of mitosis, the vital process of cell division that enables growth, repair, and maintenance in living organisms. We delve into the stages of mitosis, including interphase and cytokinesis, and discuss the crucial role of DNA replication in ensuring identical cells. Examples from various organisms highlight the diversity of chromosome numbers and cell division mechanisms. Discover how signals initiate cell division and why preparation is critical for successful mitosis. Understand plant versus animal cell division nuances for a complete picture of biological growth.

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Understanding Mitosis: The Process of Cell Division and Growth

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  1. How do you grow? Give examples and be specific. Welcome Back!!!!!!!!!!! • Word of the Day: tangent (‘tan jent) adjective - touching at only one point • In the middle of her discussion of her dog’s symptoms with her vet, she went off on a tangent about her pet’s cute behavior.

  2. Cell Division (Mitosis)

  3. Mitosis Basic Cell Reproduction

  4. What if there was no more Mitosis?

  5. Reasons for Mitosis: • Generate new cells for: • Growth • Repair • Maintenance

  6. DNA • Deoxyribonucleic acid • During mitosis, DNA gets reorganized from messy, spaghetti-like CHROMATIN into organized, neat CHROMOSOMES! • Humans have 46 chromosomes (23 from your mom, 23 from your dad)

  7. Chromosome number Just the way the DNA is packaged! How many do certain organisms have?? Amoeba= 50 Cat = 32 Goldfish =94 Earthworm= 36 Human = 46

  8. Neat & tidy chromosome Relaxed chromatin

  9. Chromosome structure • After DNA replication the chromosomes become visible by condensing. This is the beginning of mitosis Chromosomes= 2 sister chromatids and a centromere holding them together (see next page!)

  10. Chromosome

  11. Neat & tidy chromosome Relaxed chromatin

  12. What initiates cell division? • A cell or cells that need to undergo cell division receive a signal to begin division QUESTION: What do you think are examples of division signals?

  13. Signal Received. What happens next? • The cell must prepare for division. • Assuming you are a cell that has just received a division signal, turn to your neighbor and explain what you think you would need to do in order to make an exact replica of yourself. Your Turn!

  14. Preparation - Interphase. • Interphase is the preparation stage for a cell going through division • During interphase, 3 main preparations occur: • Growth • DNA replication (4692 Chromosomes)*IN HUMANS • New organelles and cellular materials are made (proteins made in ribosomes!

  15. Interphase G1 G1: Growth 1 S: Synthesis G2: Growth 2 S

  16. Cell Cycle= interphase and mitosis • Interphase= the “getting ready” period between cell divisions. Contains G1, S, and G2 • G1= Gap one phase. Cell grows to be able to divide. • S Phase= DNA synthesis • G2= Gap two phase. More growth! Specifically, the growth of new cell organelles and materials required for cell division

  17. Why is interphase so important? • A cell must prepare accurately in order to divide into two identical cells • DNA must be replicated properly so that both cells have the same genetic material (46  92  46) *IN HUMANS • The cell must grow and make new organelles/cellular material in order to give half to the new cell

  18. Preparation complete! • The cell is now ready to undergo mitosis!

  19. Steps of Mitosis Prophase -Microtubules start to form -Nuclear envelope starts to disappear 2. Metaphase -Chromosomes align at the center of the cell (metaphase plate) -Spindles attach to the chromosomes (each chromatid)

  20. Steps of Mitosis 3. Anaphase -Spindle fibers shorten to pull sister chromatids apart 4. Telophase -Nuclear envelope starts to reform -Cell elongates

  21. Lets look at that again…

  22. Early Prophase

  23. Late Prophase

  24. Early Metaphase

  25. Late Metaphase

  26. Anaphase

  27. Telophase

  28. What happens during mitosis?Chromosome alignment. • The replicated chromosomes (DNA) move towards the middle • This alignment allows the chromosomes to be separated equally between the two cells • Proteins move and align the chromosomes

  29. What is the point of alignment? B. A. What would be the result of these two cells dividing?

  30. Mitosis • http://labs.bio.unc.edu/Salmon/

  31. What happens during mitosis?Physical division (Cytokinesis). • Not only is the DNA divided equally, but the new organelles and cellular material must be divided equally as well • The cell pinches or furrows in the middle then physically separates into two identical cells. (cleavage) • This phase is called cytokinesis.

  32. What is the result of mitosis? • Two identical cells (the original and a new cell) • Think of a photocopier machine: (Interphase, mitosis, cytokinesis) Original (46 chromosomes) Copy (46 chromosomes)

  33. Plant Cell Division • Plant cells divide just like animal cells EXCEPT they do not have centrioles and their cell wall causes cytokinesis to occur differently A new cell wall forms in between the two new cells in plant cells rather than furrowing/cleavage

  34. Mitosis in action! Cross section of a wound SCAB BLOOD (BLOOD CELLS) UNWOUNDED SKIN CELLS UNDERLYING BLOOD VESSEL

  35. Zooming in on one cell in the cross section… Alert! -Growth -DNA Replication -More Organelles Made Cell receiving division signal Cell undergoing mitosis

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