1. How do cells grow & reproduce?

2. In the Beginning – One Cell Most of the organisms start out as one cell Humans start out as a single cell, the zygote, formed by uniting a sperm and egg The zygote divides to make trillions of cells During the process of dividing, cells become specialized to function in the various tissues and organs of the body = differentiation Mitosis is the process of cell division in eukaryotic cells

3. The Cell Cycle = Sequences of growth and division of a cell Two main parts: 1.Interphase – growth phase; takes most of the time 2.Mitosis – cell division phase G1 M M G2 S S Interphase

4. G1 M M G2 S S The Cell Life Cycle Gap 1 - Doubling of cell size, increase in the number of organelles, regular cellular activities S - Synthesis of DNA Gap 2 - Final preparation for division Mitosis - Cell division G1, S, & G2 = Interphase = busy time

5. S phase – DNA replication Fig. 3.26

6. INTERPHASE: nuclear envelope is clearly visible chromatin = uncoiled DNA http://www.fed.cuhk.edu.hk/~johnson/photomicrographs/mitosis/animal/animal_interphase.htm nucleolus is still visible

7. Interphase Metabolic phase Cell growth DNA replication Protein synthesis Visible nucleus with CHROMATIN

8. Stages of Mitosis Interphase Anaphase Telophase Metaphase Mitotic spindle Prophase Nucleus with chromatin Equator of the cell Condensed chromosomes Disappearing nuclear membrane Poles of the cell Mother cell Two daughter cells

9. PROPHASE chromosomes become visible nuclear envelope disappears nucleolus disappears http://www.ac-dijon.fr/pedago/svt/documents/mitose/prophase.gif

10. Prophase Centrioles move to the opposite sides of cell Spindle fibers from centrioles connect with chromosomes

11. Prophase

12. METAPHASE http://iccbweb.med.harvard.edu/mitchisonlab/Pages/mt.html

13. METAPHASE http://www.chembio.uoguelph.ca/educmat/chm736/cycletx.htm chromatids spindle centriole Chromosomes line up at the equator of the cell Each chromatid is attached to a separate spindle fiber by its centromere

14. Metaphase

15. Nature (408. 423, 2000). chromatids spindle centriole http://www.blc.arizona.edu/courses/181gh/Lectures_WJG.01/mitosis_F.01/mitosis.html

16. ANAPHASE http://www.univ-orleans.fr/SCIENCES/BIOCHIMIE/MMC/accueil.htm

17. Conly Rieder http://www.wadsworth.org/BMS/SCBlinks/WEB_MIT2/HOME.HTMhttp://www.wadsworth.org/BMS/SCBlinks/WEB_MIT2/HOME.HTM ANAPHASE earlylate

18. http://www.blc.arizona.edu/courses/181gh/Lectures_WJG.01/mitosis_F.01/mitosis.html ANAPHASE Chromatids separate and migrate to opposite poles

19. Anaphase

20. TELOPHASE Daughter Nucleus Daughter Nucleus Spindles dissolve

21. Telophase Chromosomes uncoil Two identical nuclei are formed (DNA is in the chromatin form) Nuclear membrane & nucleolus reappear

22. Cytoplasmic Division: Cytokinesis Division of a cell’s cytoplasm to form two identical cells Usually begins in late anaphase Interphase begins when cytokinesis is complete

23. Replication Chromosomes, Chromatids & Centromeres Centromere Chromosome arm Identical chromatid (sister chromatid) Chromatid Anaphase A packaged chromosome Two identical chromosomes DNA doubling during S- phase Joins sister chromatids

24. Results of Mitosis: Two new diploid cells with chromosomes that are identical to those of the parent cell Hmm… Why is it necessary for a cell’s chromosomes to be distributed to its daughter cells in such a precise manner?