1.  Chapter 12~ The Cell Cycle

2. 3 Key Roles of Cell Division  Reproduction  Growth and development  Tissue renewal and repair

3. Cell division vocabulary  Genome  Cell’s genetic information  Made of several DNA molecules each one containing and enormous amount of information  Chromosomes are condensed coils of DNA that are found in eukaryotic cells right before cellular division takes place  Types of Eukaryotic cells  Somatic (body cells) cells  Diploid (2n): 2 sets of chromosomes  Gametes (reproductive cells): sperm and egg cells  Haploid (1n): 1 set of chromosomes

4. Chromosomes components  Chromosomes are tightly coiled chromatin  Chromatids: replicated strands of a chromosome  Each chromosome has two sister chromatids  Centromere: narrowing “waist” of sister chromatids ( where they are most closely attach together)  Kinetochore: Structure of proteins associated with specific a section of chromosomal DNA at the centromere

6. Chromatin structure is based on levels of DNA packing  Histones ( 1 st level)  Proteins- DNA wraps around the histone moleulces  Nucleosomes ( 2 nd level)  Beads on a string- The whole complex of DNA and several histone proteins  30- nm fiber ( 3 rd level)  String of nucleosomes coil to from chromatin fiber  Looped Domains ( 4 th level)  30- nm fiber further folds and creates looped domains  Chromosome ( 5 th level)  Looped domains fold even further to produce a chromosome

8. Types of cellular division  Somatic cell division  Mitosis: nuclear division  Cytokinesis: cytoplasm division  Gamete cell division  Meiosis: gamete cell division

9. The Mitotic Cell Cycle  Mitosis ( division of somatic cells) is one part of the cell cycle of all cells  Cell cycle  Interphase  G1- cell resting and growth  S – DNA synthesis ( replication )  G2 – grows and gets ready for cell division  M Phase  division of the nucleus and the cytoplasm

11. Mitosis and spindle formation  Before mitosis can begin the spindle must be formed  Centrosomes  Have pairs of centrioles  Centrosomes spin the spindle microtubules which will eventually pull the sister chromatids apart during anaphase

12. Mitosis ( M phase of cycle)  5 Phases in mitosis  Prophase  Prometaphase  Metaphase  Anaphase  Telophase and cytokinesis

13. Prophase  Chromosomes visible  Nucleoli disappear  Sister chromatids  Mitotic spindle forms  Centrosomes move

14. Prometaphase  Nuclear membrane fragments  Spindle interaction with chromosomes  Kinetochore develops  Where spindle fibers attached to centromere of chromosome

15. Metaphase  Centrosomes at opposite poles  Centromeres are aligned  Kinetochores of sister chromatids attached to microtubules (spindle)

16. Anaphase  Paired centromeres separate; sister chromatids liberated  Chromosomes move to opposite poles  Each pole now has a complete set of chromosomes

17. Telophase  Daughter nuclei form  Nuclear envelopes arise  Chromatin becomes less coiled  Two new nuclei complete mitosis

18. Cytokinesis  Cytoplasmic division  Animals: cleavage furrow  Plants: cell plate

19. Control of cell cycle  Cell Cycle Check Points 1. Cell Growth Check point (G1)- Checks to see if conditions are right for cell to divide.  If cell gets the “okay” here it will most likely divide

20. Control of cell cycle 2. DNA Synthesis Check Point ( G2)- DNA replication is checked 3. Mitosis Checkpoint- Triggers the exit from mitosis and back into the G 1 phase.  If control of the cell cycle is lost you get things like cancer in which there is uncontrolled growth and division

21. Control of cell cycle  Controlled mostly by proteins within the cell  Cyclin- dependent kinases  Regulatory molecules that are proteins of two main types  Protein kinases- enzymes that activate or inactivate other proteins by phosphorylating them  Present at a constant concentration within the cell but will only be activated in the presence of cyclin ( other protein)

22. Control of the cell cycle  Cyclin-Cdk complexes  MPF- Maturation promoting factor ( M- phase promoting factor)  Triggers the cells passage from the G2 checkpoint into the M phase  Results when cyclin that accumulated during the G2 phase meets with the Cdk to make the MPF complex  MPF switches itself off by destructing the cyclin that the Cdk is attached to rendering it inactive and putting the cell back into the G1 phase

23. Cell Cycle regulation  Growth factors- proteins released by certain body cells  Density- dependent inhibition- too many cells the cell will stop dividing  Anchorage dependence