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Understanding the Cell Cycle: Mitosis and DNA Replication

Explore the stages of the cell cycle, from DNA replication to mitosis, and its significance in organism growth. Answer key questions and learn about the different phases of cell division.

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Understanding the Cell Cycle: Mitosis and DNA Replication

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  1. Cell Cycle (Cell Division)

  2. The student is expected to:5A describe the stages ofthe cell cycle, includingdeoxyribonucleic acid (DNA)replication and mitosis, and theimportance of the cell cycle to thegrowth of organisms

  3. Write these questions and answer them. • Where are chromosomes found? • How many chromosomes or pairs of chromosomes do we have in each of our cells? • How do we make new human organisms? • How many chromosomes do sperm cells have? How about egg cells? • When a sperm fertilizes an egg, how many chromosomes are present? How many cells are present? • How does the fertilized egg become a baby?

  4. Why do cells divide? • Increased volume  increased demand • Volume  exponential growth • Surface area  doubles • Lack of surface area triggers cell division

  5. Developing multicellular Organism.

  6. KEY CONCEPT Cells divide during mitosis and cytokinesis.

  7. cells divide at different rates. • The rate of cell division varies with the need for those types of cells. • Some cells are unlikely to divide (G0).

  8. Rates of Cell Division • Rapid • Skin • Digestive tract • Bone marrow • Replace worn out or broken down cells • Rarely • Muscle • Nerve (slowest) • Stay in G0 phase

  9. Cell growth is coordinated with division. • Cells that must be large have unique shapes. • Surface area must allow for adequate exchange of materials.

  10. Cell Cycle has 3 main functions

  11. 1. Growth

  12. 2. Replacement and 3. Repair

  13. Cell Cycle • Interphase(preparation for cell division) • G1 – Growth 1 • S - Synthesis • G2 - Growth 2 • Mitosis(Division of the nucleus) • Prophase • Metaphase • Anaphase • Telophase • Cytokenesis (Division of the cytoplasm)

  14. Interphase Centrioles 75% of cell’s life spent here Includes G1, S, and G2 Nucleolus

  15. InterphaseG1 – Growth 1 • Cell doubles in size • Some organelles (ribosomes & mitochondria) double in number. • Cells that don’t duplicate, stay at this phase • Go

  16. InterphaseS – Synthesis (to make) • DNA Replication • DNA makes a copy of itself so that each “new” cell has a complete set.

  17. InterphaseG2 – Growth 2 • Spindle fiber are assembled. • The rest of the needed organelles are produced. • The cell is now ready to divide!!!

  18. Before we go into Mitosis, we are going to talk about the S sub-phase and exactly what happens there! DNA Replication

  19. DNA Replication • So that identical copies of the cell’s genes, can be passed on to each new cell. • DNA Replication occurs during the S sub-phase of Interphase.

  20. When referring to individual sides, they are called sister chromatids. Chromosome • Chromosome • Single Copy • Chromosome • Double Copies • Has gone through DNA Replication – so that each cell gets a complete set of 46. Centromere- hold copies together

  21. Which of these is ready to go through cell division?

  22. DNA andhistones SupercoiledDNA DNA doublehelix Chromatin Chromosomes condense at the start of mitosis. • DNA wraps around proteins (histones) that condense it.

  23. Mitosis – Division of the nucleus (DNA) • Remember: During Interphase the S sub-phase, we made a copy of DNA and in Mitosis we are separating those copies.

  24. Review:Interphase Chromatin DNA Replication has occurred but chromosomes are uncoiled

  25. Mitosis – Prophase 1. Nuclear Envelope begins to break down 2.Chromosomes coil up & condense 4.Spindle Fibers are put together 3.Centrioles migrate to opposite poles

  26. Mitosis – Metaphase 1.Chromosomes line up at the equator 2.Centrioles at opposite poles 3. Spindle Fibers attach to chromosomes at the kinetochore

  27. Anaphase • Centromeres split • Chromatids pulled apart  now called chromosomes

  28. Mitosis – Anaphase(cytokenesis begins here) 2.Spindle Fibers pull Sister Chromatids apart to opposite poles 1.Plasma membrane elongates 3.Sister Chromatids are now chromosomes of the new cell forming Anaphase is Critical to chromosomal distribution

  29. 3rd Phase of Cell CycleCytokenesis • Cytokenesis begins with Anaphase and continues to finish with Telophase. • Cytokenesis is the division of the cytoplasm ( organelles and cytosol) • It is not an even distribution thus the 2 daughter cells at the end are not completely identical.

  30. Mitosis – Telophase 2 5 1 3 4

  31. Telophase is the opposite of Prophase • 1. Nuclear Envelope is reformed. • 2. Chromosomes uncoil forming Chromatin. • 3. Only 1 centriole left – the other will be made in Interphase. • 4. Spindle Fibers are dissolved. • 5. Cleavage Furrow continues to pinch until the cell is divided to form 2 daughter cells with identical DNA.

  32. In animal cells, the membrane pinches closed. • In plant cells, a cell plate forms. • Cytokinesis differs in animal and plant cells.

  33. Controlling Cell Growth • Stop when touching • Can resume when space (injury) • Contact inhibition • Stop when cannot absorb enough nutrients • Uncontrolled growth: cancer

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