Cell Growth and Reproduction

1. Cell Growth and Reproduction

2. Cells cannot survive if there is not enough DNA • Cells divide before they become too big to function properly

3. Cell Reproduction • Cell division is a process in which new cells are produced from one cell • Diagram: • 2 daughter cells are identical to the original parent cell

4. Discovery of Chromosomes • before cells divide, several short, stringy structures suddenly appear inside the nucleus • vanish right after the cell divides • called chromosomes • contain DNA • carriers of genetic material • copied and passed through generations of cells

5. Has 2 halves called sister chromatids • Held together by a centromere

6. Chromosomes usually exist as chromatin • long strands of DNA wrapped around histone proteins • Coils up into visible chromosomes during mitosis (cell division)

7. Cell Cycle • Sequence of the growth and division of a cell • 2 general periods Mitosis G2 G1 S

8. Growth (called Interphase) • Majority of cell’s life spent in this phase • Cell grows in size • Carries on metabolism • Chromosomes are duplicated

9. Interphase • Busiest phase • Divided into 3 parts • G1 Phase: rapid growth and metabolic activity • Cell grows • High production of proteins • S Phase: DNA synthesis and replication • Cell copies its chromosomes • G2 Phase: Cell prepares for division • Organelles are made • Centrioles replicate

10. Division (called Mitosis) • Nuclear division • 2 daughter cells are formed from 1 parent cell

11. Prophase • 1st phase (longest) • chromosomes become visible • centrioles separate to opposite sides of the nucleus (in animal cells only) • nucleus begins to disappear • nuclear envelope and nucleolus begin to disintegrate • spindle forms  role in separating sister chromatids

13. Metaphase • Chromosomes become attached to the spindle fibers by a centromere • Chromosomes begin to line up in the middle of the cell • Very short phase (lasts a few minutes)

15. Anaphase • Centromeres split apart • Separation of sister chromatids from each other • Shortening of spindle fibers • Individual chromosomes result in 2 groups

17. Telophase • Final phase of mitosis • Chromosomes unwind (become a tangle of material) • Spindle breaks down • Nucleolus reappears • New nuclear envelope forms around the chromosomes • Membrane forms between 2 nuclei

19. Cytokinesis • Cell’s cytoplasm divides • Usually occurs at the same time as telophase • Animal cells: plasma membrane pinches in along the middle of the cell • Plant cells: • Have rigid cell wall • Cell plate goes across the center of the cell • Cell membrane forms around each cell • New cell wall forms on each side of cell plate

20. Animal Cell

21. Plant Cell

22. Control of Cell Cycle • Cells can lose control of the cell cycle • Can result from failure o produce certain enzymes, overproduction of enzymes, or producing enzymes at the wrong time • leads to uncontrolled cell division (called cancer) • Genes: segment of DNA that controls production of proteins like enzymes

23. Cancer • Result of uncontrolled cell division • Forms masses of tissue called tumors • Deprives normal cells of their nutrients • Metastasis: cancer spreads throughout body infecting circulatory system • 2nd leading cause of death • Can affect any tissue in the body

24. Environmental Cigarette smoke Air and water pollution Exposure to UV radiation Damages genes that controls cell cycle Genetic Viral diseases and infections can damage genes Causes of Cancer

25. Cancer Prevention • Diets low in fat and high in fiber • Vitamins and minerals