1. Chapter 12

2. Genetic Material  Typical cell is ~2 m in length (~250,000x’s the length of the cell) Total genetic material (DNA) in the cell is it’s genome  Chromosomes Carries the cells genetic information from one generation to the next. Made of DNA and proteins

3. Genetic Material  Chromatin DNA and histone proteins wrapped together Keeps the DNA compacted

4. Genetic Material During Cell Division  Chromatids One of two identical “sister” parts of a duplicated chromosome  Centromeres Area where the chromatids of a chromosome are attached most closely

5. Cell Cycle  Interphase Period of the cell cycle between cell divisions  Cell cycle During the cell cycle, a cell grows, prepares for division, and divides to form two daughter cells, each of which then begins the cycle again

6. Cell Cycle  G 1 phase Cell growth  S phase DNA replication  G 2 phase Preparation for mitosis  M phase Cell division (mitosis and cytokinesis)

7. Mitotic Phase  Mitosis Division of the cell nucleus Five phases (PPMAT) ○ Prophase, Prometaphase, Metaphase, Anaphase, and Telophase

8. The Mitotic Spindle  Centrosome Point at which the spindle microtubules begin to form Contains the centrioles Move apart during prophase/prometaphase Form an aster ○ Short microtubules extending from the microtubules

9. The Mitotic Spindle  Kinetochore Proteins that are associated with specific DNA at the centromere Face opposite directions Site of attachment for some of the spindle fibers “Tug of war” begins to line up the chromatids on the equator for metaphase

10. Mitosis  Prophase Chromatin fibers become more tightly coiled Nucleoli disappears Mitotic spindles begin to form Centrosomes move to opposite poles

11. Mitosis  Prometaphase Nuclear envelope disappears Microtubules invade the nuclear area Chromosomes even more condensed Chromatids now have a kinetochore ○ Some spindle fibers attach

12. Mitosis  Metaphase Centrosomes are at opposite poles Chromosomes line up across the metaphase plate Each chromosome is connected to a spindle fiber at the kinetochore

13. Mitosis  Anaphase Sister chromatids separate into individual chromosomes Chromosomes move toward opposite poles

14. Mitosis  Telophase Chromosomes gather at the poles and lose their shape New nuclear envelopes surround each set of chromosomes Nucleoli reappear

15. Cytokinesis  Cytokinesis Begins with a cleavage furrow Division of the cytoplasm Each daughter cell has an identical set of chromosomes

16. Binary Fission  Prokaryotic cell division Cell doubles in size Origin of replication ○ Point where the DNA begins to replicate – two origins ○ The points move towards opposite poles

17. Chromatid Movement  2 different mechanisms “Pacman” – chromosomes walk along the microtubule Reel in – the chromosomes are reeled by motor proteins at the spindle poles

18. Cell Cycle Regulation  Cycle is controlled by a set of molecules and checkpoints Checkpoints are where ‘stop” and “go ahead” signals occur Three important checkpoints: G 1, G 2, M ○ G 1 is called the “restriction point” – if go-ahead given the cell will complete the cycle ○ If no go-ahead signal-cell goes to G 0

19. Cyclins and Cdk’s  Regulatory molecules are typically proteins Cyclins Cyclin-dependent kinases ○ Many different Cdk’s regulate different check points in the cell cycle

20. Cancer  Loss of control of the cell cycle  Can go on dividing indefinitely HeLa cells  Begins with transformation of a normal cell  Tumor formation Benign Malignant ○ Metastasis