1. Cellular Reproduction The Cell Cycle & Mitosis

2. 9 - Ch.9 – Cellular Reproduction 9.1 – Cellular Growth

3. 9 - Ch.9 – Cellular Reproduction 9.1 – Cellular Growth Genetic Material Some key terms… Genome – All of the cell’s DNA/inheritable traits Chromosomes – Smaller packages of DNA molecules Somatic Cells – Body cells which have a full set of chromosomes (2n) Gametes – Reproductive cells which have ½ the number of chromosomes (n) Chromatin – DNA and protein molecules (histones) Each human cell has about 2 meters of DNA in its nucleus It all has to be copied precisely before a cell can divide (reproduce) All Eukaryotes have a specific # of chromosomes in each cell nucleus

4. 9 - Ch.9 – Cellular Reproduction 9.1 – Cellular Growth Cells duplicate their genetic material before they divide, ensuring that each daughter cell receives an exact copy of DNA

5. 9 - Ch.9 – Cellular Reproduction 9.1 – Cellular Growth Cell Cycle (The life cycle of a cell) Broken into 2 parts Interphase Mitosis Period when the cell grows, carries out its cellular functions and replicates DNA in preparation for cellular division Period when the nucleus & nuclear material divides. Cytokinesis occurs near the end of mitosis. It is the dividing of the cytoplasm.

6. 9 - Ch.9 – Cellular Reproduction 9.1 – Cellular Growth Cell Cycle (The life cycle of a cell) Period when the cell grows, carries out its cellular functions and replicates DNA in preparation for cellular division Period when the nucleus & nuclear material divides. Cytokinesis occurs near the end of mitosis. It is the dividing of the cytoplasm. Broken into 2 parts Interphase Mitosis

7. 9 - Ch.9 – Cellular Reproduction 9.1 – Cellular Growth Interphase G 1 (1 st Gap) Phase – Growth & normal cell function S (Synthesis) Phase – DNA is copied G 2 (2 nd Gap) Phase – Cell prepares for division of its nucleus Protein for microtubules is synthesized Additional cell growth Cell “checks” the DNA to be sure that it was copied correctly so that mitosis can begin

8. Mitosis Can be broken down into 5 phases Prophase Prometaphase Metaphase Anaphase Telophase Division of the nuclear material

9. 9 - Ch.9 – Cellular Reproduction 9.2 – Mitosis & Cytokinesis PROPHASE Chromatin condenses Nucleolus disappears Spindle fibers begin to form Centrioles separate

10. 9 - Ch.9 – Cellular Reproduction 9.2 – Mitosis & Cytokinesis PROMETAPHASE Nuclear envelope fragments Centrioles near the poles Chromosomes begin to attach to the spindle fibers at the kinectochore (a protein located at the centromere)

11. 9 - Ch.9 – Cellular Reproduction 9.2 – Mitosis & Cytokinesis METAPHASE Longest stage of mitosis (~20min.) Duplicated chromosomes align at the metaphase plate (equator of the cell)

12. 9 - Ch.9 – Cellular Reproduction 9.2 – Mitosis & Cytokinesis ANAPHASE Shortest stage of mitosis (~2min.) Sister chromatids are separated and are pulled to the poles The cell elongates By the end of anaphase each pole has one copy of each chromosome

13. 9 - Ch.9 – Cellular Reproduction 9.2 – Mitosis & Cytokinesis TELOPHASE Nuclear membranes form Nucleoli reappear The chromosomes become less condensed (unwind)

14. 9 - Ch.9 – Cellular Reproduction 9.2 – Mitosis & Cytokinesis Mitosis in Plant Cells

15. 9 - Ch.9 – Cellular Reproduction 9.2 – Mitosis & Cytokinesis CYTOKINESIS Starts during telophase

16. 9 - Ch.9 – Cellular Reproduction 9.3 – Cell Cycle Regulation Cell Cycle Regulation G 1 checkpoint Ensures… Enough nutrients Large enough to divide If “go” signal is given cell will divide If go signal is not given cell will enter the G 0 (non- dividing) phase G 2 checkpoint Ensures… DNA was copied correctly in the S-phase M checkpoint Ensures… All sister chromatids are connected properly at the kinetochore

17. 9 - Ch.9 – Cellular Reproduction 9.3 – Cell Cycle Regulation The Cell Cycle Clock Controlled by cyclins and cyclin-dependent kinases Proteins that build up and then degrade at certain points in the cell cycle (Cdk) Enzymes the cyclins bind to in order to initiate the next the next phase in the cell cycle

18. 9 - Ch.9 – Cellular Reproduction 9.3 – Cell Cycle Regulation The Cell Cycle Clock Internal and external factors trigger cell division Internal Growth factors - proteins released by certain cells that stimulate other cells to divide. (Growth hormones in mammals) External Space and available nutrients An anchor point (for most animal cells)

19. Cancer… 9 - Ch.9 – Cellular Reproduction 9.3 – Cell Cycle Regulation What happens when cells lose the ability to control the cell cycle? Cells can become cancerous when a mutation occurs spontaneously or from an outside factor (carcinogen) As cells multiply a predictable series of genetic changes occur

20. 9 - Ch.9 – Cellular Reproduction 9.3 – Cell Cycle Regulation These changes ultimately lead to the mutation of two types of genes that control the cell cycle… Oncogenes and tumor-suppressor genes Benign Tumor – does not invade surrounding tissue Malignant Tumor – invades surrounding tissue and spreads via circulatory or lymph system 10 billion to 100 billion cells. Usually takes decades to cause a problem in humans