2. WHY DO CELLS DIVIDE?
• As cells grow, their volume increases faster than their surface area
• Cells that grow too large cannot take in nutrients and remove waste
• Cells that grow too large take much longer to move materials within the cell
• As organisms grow new cells are created to replace old dying ones and make the organism grow
3. THE CELL CYCLE
• Cell cycle - sequence of phases in the life cycle
of the cell
4. – Cell grows.
– DNA is replicated.
- Mitotic cell division produces daughter
cell identical to the parent.
Like prokaryotic cell cycle, in that…
Eukaryotic Cell Cycle
5. Mitosis
The Basic Phases
of a Cell’s Life:
•Interphase
•Prophase
•Metaphase
•Anaphase
•Telophase
•Cytokinesis
6. INTERPHASE
• S or Synthesis stage
• Preparation of Mitosis
• Organelles are replicated
• Longest stage of a cell’s life
• More growth
7. PROPHASE
• Chromosomes condense
• Microtubules appear in
• Nuclear membrane breaks down
• Chromatin fibers become coiled into chromosomes with
each chromosome having two chromatids joined at a
centromere.
• The two pair of centrioles (formed from the replication
of one pair in Interphase) move away from one another
toward opposite ends of the cell
8. METAPHASE
• Chromosomes are pulled to center of cell
• Line up along “metaphase plate”
• Polar fibers (microtubules that make up
• the spindle fibers) continue to extend
• from the poles to the center of the cell.
• Chromosomes align at the metaphase plate at right angles to the spindle
poles.
• Chromosomes are held at the metaphase plate by the equal forces of the
polar fibers pushing on the centromeres of the chromosomes.
9. ANAPHASE
• The third phase of Mitosis
• Diploid sets of daughter chromosomes separate
• They are pushed and pulled toward opposite poles of the
cell by the spindle fibers
• Precise alignment is critical to division
10. TELOPHASE
• The polar fibers continue to lengthen.
• Nuclei begin to form at opposite poles.
• Chromatin fibers of chromosomes uncoil.
• After these changes, telophase/mitosis is largely complete and the
genetic contents of one cell have been divided equally into two.
11. CYTOKINESES
• Physical process of cell division, which divides the cytoplasm of a
parental cell into two daughter cells.
• Signifies end of cell division
13. MEOSIS
• A division of the nucleus that reduces
chromosome number by half.
•Important in sexual reproduction
•Involves combining the genetic information of one
parent with that of the the other parent to
produce a genetically distinct individual
14. MEIOSIS
• - A single germ cell divides into four unique daughter cells.
- Daughter cells have half the # of chromosomes as parent cell, so they
considered haploid.
15. MITOSIS
• a type of cell division that results in
two daughter cells each having the
same number and kind of
chromosomes as the parent
nucleus, typical of ordinary tissue
growth.
