2.  Cell cycle: regular pattern of growth, DNA duplication, and cell division that occurs in eukaryotic cells.  Organisms use the cell cycle to grow and repair their bodies.

3. INTERPHASE Gap 1 (G 1 ): Normal growth Synththesis: DNA is copied Gap 2 (G 2 ): Cell prepares to divide MITOTIC STAGE Prophase, metaphase, anaphase, telophase CYTOKINESIS Cell divides into 2

4. Cell TypeApproximate life span Skin cell2 weeks Red blood cell4 months Liver cell300-500 days Intestine-internal lining4-5 days Intestine-muscle and other tissues 16 years The rate at which your cells divide is linked to your body’s need for those cells. Prokaryotic cells divided faster than eukaryotic cells

5. To small-not enough room for organelles To large-ratio of cell surface area to volume; cells must be able to use their surface area to absorb enough nutrients and get rid of wastes Look at the ratios on the first 2 cells. The maximum SA:V ratio is best. What are the ratios for the first 2 cells? The third cell?

6. You do need to be able to recognize the phases, but you also need to know what is happening to the chromosomes. Look at each phase. Using your knowledge of the cell cycle and the picture to the right, write a sentence for each phase listed that tells what is happening to the chromosomes and WHY it is necessary.

7. During interphase, the longest part of the cell cycle, the DNA is unwound and available for transcription of the genes. During this time it is called chromatin. During prophase the chromatin winds up into chromosomes, and remains so until the cell divides. What are chromatids? Where is the centromere?

8. Mitosis is nuclear division. Mitosis only occurs in eukaryotes. Mitosis takes place in SOMATIC cells. ‘Somatic’ is all cells except gametes (sex cells) Mitosis and cytokinesis produce 2 genetically identical daughter cells. Genetically identical cells are called clones. Mitosis animation

12. Internal and external factors regulation cell division. External factors Cell to cell contact helps regulate normal cell division Growth factors Examples are PDGF and erythropoietin Internal Factors Kinases and cyclins (proteins) Apoptosis-cell suicide

13. Regulation of the cell cycle breaks down. Cancer cells do not respond to cell-to-cell contact or to growth factors. Tumors-disorganized clumps of cells Benign-cells remain clustered together in one place Malignant-some cells can break away and travel to other parts of the body where they form tumors (Metastasis) Tumors are harmful because they do not function normally and use valuable nutrients

14. Cancer cells come from normal cells that have suffered damage to the genes that make the proteins that involved in cell cycle regulation. Oncogenes are cancer causing genes. They may be inherited. Ex. BRACA genes for breast cancer Cancer causing genes have mutations. Mutations may be inherited or arise spontaneously. Environmental factors can play a role: Mutagens cause mutations UV radiation Carcinogens are cancer causing chemicals Cigarette smoke; air pollution

16. 2 types of reproduction are sexual and asexual: Sexual-2 parents, results in genetically unique offspring Asexual-1 parent; offspring are clones of the parent Eukaryotic organisms can asexually reproduce by mitosis. Prokaryotic organisms do not have a nucleus. They can asexually reproduce by BINARY FISSION. Organism copies its 1 chromosome and then splits in half.

17. Multicellular organisms depend on interactions among different cell types. Specialized cells perform different functions. If you have the same DNA in all of your cells, how can they be so different?

18. Stem cells are a unique type of body cell. They can: Divide and renew themselves for long periods of time. Remain undifferentiated in form (what does this mean?) Develop into a variety of specialized cell types. Stem cell classification: Totipotent-can grow into any other kind of body cell Embryonic (first few cell divisions after fertilization) Pluripotent-can grow into any cell type except for totipotent stem cells Multipotent-can grow only into cells of a closely related cell family.

19. Adult stems cells Multipotent (but new research shows…..) Partially undifferentiated cells Found scattered in the body tissues Cord blood stem cells Major advantage-can be taken from patient, grown in culture, and put back it for treatment Major disadvantages-few in number, difficult to isolate, contain more DNA abnormalities Embryonic stem cells NOT TAKEN FROM ABORTION CLINICS These are donated by fertility clinics from in vitro fertilizations that will not be used. Advantage-totipotent Disadvantage-may be rejected by recipient