2. Brain Pop When something divides, what happens to it?

3. Mitosis

4. Cell Division: Mitosis Dividing cells Mitosis and the cell cycle 4 main stages of mitosis 4 main stages of mitosis A. Prophase A. Prophase B. Metaphase B. Metaphase C. Anaphase C. Anaphase D. Telophase D. Telophase

5. Prokaryotic Cell Division Bacterial cells reproduce by Binary Fission No Nucleus Much simpler process than in eukaryotic organisms (why?)

6. Prokaryotic (Single) Cell Division 1. Begins with DNA replication (why?); 2. Followed by elongation of cell, and separation between the two halves. 3. Results in two new cells that are identical (clones) of original cells

7. Eukaryotic (has nucleus) Cell Division 1. Mitosis…cells Grow or replace dead or worn out cells, or to repair wounds Grow or replace dead or worn out cells, or to repair wounds Any cell but sex cells Any cell but sex cells sperm & egg)

8. DNA and Cell Division During cell division, the genetic material DNA, needs to be copied and divided evenly between the two new cells During cell division, the genetic material DNA, needs to be copied and divided evenly between the two new cells

9. Eukaryotic Chromosome Structure DNA in cells is divided into long chains called chromosomes (CZ) (“volumes” of DNA) DNA in cells is divided into long chains called chromosomes (CZ) (“volumes” of DNA) During mitosis, chromosomes fold up and condense During mitosis, chromosomes fold up and condense

10. Eukaryotic Chromosomes Chromosomes must be replicated before cell division. Chromosomes must be replicated before cell division. Sister chromatids: Sister chromatids: two identical copies (chromatids) formed by the replication of a single chromosome

11. Chromosome structure At the start of mitosis they condense & take a form At the start of mitosis they condense & take a form The replicated chromosomes stay together and are called sister chromatids The replicated chromosomes stay together and are called sister chromatids Sister chromatids are attached at the centromere. Sister chromatids are attached at the centromere.

13. The Cell Cycle: (1) Interphase When a cell is dividing and is building its chromosomes, then it is said to be in Interphase

14. III. Stages of mitosis

16. The Spindle Fibers Moves chromosomes during mitosis Moves chromosomes during mitosis In both plant and animal cells, spindle fibers originate from centrosomes; in animal cells, from centrioles In both plant and animal cells, spindle fibers originate from centrosomes; in animal cells, from centrioles

17. (2) Prophase Chromosomes continue to condense Chromosomes continue to condense Centrioles move to each pole of the cell Centrioles move to each pole of the cell Spindle fibers are assembled Spindle fibers are assembled Nuclear envelope dissolves Nuclear envelope dissolves

18. (3) Metaphase Microtubules pull the chromosomes to align them at the center of the cell Microtubules pull the chromosomes to align them at the center of the cell Metaphase plate: imaginary path through the center of the cell where the chromosomes line Metaphase plate: imaginary path through the center of the cell where the chromosomes line

19. (4) Anaphase The centromeres separate The centromeres separate Spindle fibers pull sister chromatids apart toward the poles Spindle fibers pull sister chromatids apart toward the poles

20. (5) Telophase Spindle fibers disassembles Spindle fibers disassembles Nuclear membrane forms around each set of sister chromatids Nuclear membrane forms around each set of sister chromatids Chromosomes begin to uncoil Chromosomes begin to uncoil Nucleolus reappears in each new nucleus Nucleolus reappears in each new nucleus

21. (6) Cytokinesis Usually occurs between late anaphase and end of telophase Usually occurs between late anaphase and end of telophase Two mechanisms Two mechanisms 1. Cell plate formation (plants) 2. Cleavage (animals)

22. Cytokinesis: Animal Cell

23. Cytokinesis: Plant Cells Cytokinesis: Plant Cells