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Biology

Biology. The Cell Cycle & Mitosis Video. Cell Cycle. Cell division occurred in: Reproduction (asexual vs. sexual) Overall growth Repair (skin cells for example) Dividing cells follow something called the cell cycle . Only 10% of the cell cycle is devoted to cell division (mitosis).

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Biology

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  1. Biology The Cell Cycle & Mitosis Video

  2. Cell Cycle • Cell division occurred in: • Reproduction (asexual vs. sexual) • Overall growth • Repair (skin cells for example) • Dividing cells follow something called the cell cycle. • Only 10% of the cell cycle is devoted to cell division (mitosis). • The other 90% is devoted to cell growth, DNA replication and preparation for cell division.

  3. Cell Cycle cont’d 4. Cell division 3. Cell prepares to divide 1.Cell Growth 2. Synthesis: DNA replicates

  4. Interphase • The longest stage of the cell cycle. • During Interphase, the cell carries out all life functions except division. They include • Growth • Cellular respiration • Other special functions. • At this stage, the genetic material (DNA), is in very long invisible strands inside the nucleus (chromatin). • When the cell prepares for division, the DNA is replicated and more organelles are formed.

  5. Chromatin Centrioles: “Barrel” shaped organelles used in division.

  6. DNA • Stands for Deoxyribonucleic Acid. • Contains all the genetic material for a living organism. • Humans have 23 pairs of chromosomes for a total of 46: • 23 from mom, 23 from dad • The entire DNA molecule contains all genetic material in a single undivided form.

  7. Cell Division • Occurs in two stages: • Mitosis: The division of contents of the nucleus. 4 steps: • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis: The division of the rest of the cell including: • Cytoplasm, organelles and cell membrane. • Each division produces two identical daughter cells.

  8. Prophase • Long strands of DNA condense into a compact form called chromosomes. • Chromosome contains a portion of DNA. • Since DNA was copied during interphase, each chromosome contains a pair of identical strands called sister chromatids. • The chromatids are held together by centromeres. • Nuclear membrane dissolves during this time. • Centrioles (organelles used in pulling cells apart) migrate to opposite sides of cell. • Spindle fibres are released by the centrioles to attach to chromosomes.

  9. Nuclear Membrane Centromere Spindle Fibres Sister Chromatids

  10. Metaphase • Chromosomes line up in the middle of the cell. • Spindle fibres from centriole attach to centromeres of each chromosome. • All must be in line for mitosis to continue.

  11. Attached spindle fibres Sister chromatids lined up

  12. Anaphase • Centromere splits and the sister chromatids separate. • They are now called daughter chromosomes. • They are pulled by spindle fibres to opposite sides of the cell.

  13. Daughter chromosomes

  14. Telophase • Final stage of mitosis. • Daughter chromosomes stretch out, become thinner, and are no longer visible. • Turn back into chromatin. • A new nuclear membrane forms around each area of chromatin. • Cell appears to have two nuclei.

  15. Daughter chromosomes stretching out

  16. Cytokinesis • The final stage of cell division. • Cytoplasm divides producing two genetically identical daughter cells. • Different for each type of cell: • Animal cell: Cytoplasm pinches in half. • Plant cell: Plate between two cells turn into a cell wall.

  17. Chromatin Two daughter cells

  18. Checkpoints in Cell Cycle • Cell division is a very complicated and closely monitored process by the cell. • Specialized proteins in the cell monitor progress. The cell will not divide if: • Cell not growing properly. • DNA has not been replicated • DNA is damaged • If the DNA is damaged, cell may either repair it or destroy itself via the lysosome (“suicide sac”).

  19. References • Edupic Graphical Resource: Cells • http://www.edupic.net/cells.htm

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