2. Cellular Basis of Inheritance Chapter 9

3. Cells come from other cells Repair Growth Reproduction –Asexual Reproduction –Sexual Reproduction

4. Sexual Reproduction Genetic Material comes from 2 parents

5. Asexual Reproduction Genetic Material comes from 1 parent –Budding –Cloning –Fragmentation –Sporulation

6. Binary Fission (Prokaryotes way of Asexual Reproduction) Cell division in prokaryotes produce 2 identical daughter cells

7. The Cell Cycle Sequence of growth and division of a cell Interphase = period of growth Mitosis = period of nuclear division Cytokinesis = period of cell division Cell Cycle Movie

8. Limits on Cell Size Diffusion – becomes slow and inefficient as the cell becomes larger Surface Area/Volume Ratio – as a cell increases, its volume increases faster than its surface area DNA content – if a cell doesn’t have enough DNA to program its metabolism, it cannot survive

9. Chromosome Structure Chromatin - Uncondensed form Genetic material spends most of its time as chromatin During prophase, the chromatin material coils up and condenses to become a chromosome (coiled form of DNA)

10. Chromosome Structure Chromosomes - condensed rod shaped structures made of coiled DNA, (only seen in mitosis phase)

11. Chromosome Structure The DNA wraps around a histone core to form bead like structures known as nucleosomes This occurs during prophase Histones – proteins that help DNA coil

12. Chromosome Structure The nucleosomes coil even more The coils become the chromosome

13. From smallest to most coiled is the following –Double helix –DNA and histone protein –Coil –Super coil –Chromosomes

14. Centromere Each half of a replicated chromosome is called a chromatid Sister chromatids: The 2 identical halves of the double structure are sister chromatid; exact copies of each other Centromere: site where sister chromatids are adjoined

15. Chromosome or chromatid? 1 chromosome 1 chromatid 1 chromosome (doubled) 2 chromatids (sisterchromatids) Replication

16. Mitosis and Meiosis How and Why Cells Divide

17. Onion root

18. Interphase G 1 phase= Growth phase S phase = synthesis phase – make copy of DNA G 2 phase – Growth and cell maintenance for preparation of division occurs: - for example copying organelles

19. Interphase Gene replication occurs Cell maintenance occurs: –make ATP –excrete wastes –make proteins –produce new organelles

20. Prophase Chromatin coils up into visible chromosomes

21. Prophase Centrioles begin to migrate to opposite sides of the cell Nucleus begins to dissappear as nuclear envelope and nucleolus disintegrate

22. Prophase Spindle fibers – form between centrioles - And attach to chromosom es

23. Metaphase Chromosomes line up at the center of the cell (along the equator) (shortest phase)

24. Anaphase Chromatids split and one is pulled to each of the poles; centromere first Each chromatid is identical One copy of each chromosome goes to each side (pole)

25. Telophase Final phase of mitosis Chromatids reach opposite ends of the cell Opposite events of prophase: –chromosomes unwind into chromatin –spindle breaks down –nuclear envelope forms around 2 new sets of chromosomes (to create 2 new nuclei) –nucleolus forms in each nucleus Cytokinesis begins (before telophase is finished)

26. End of Mitosis Nuclei go back into interphase Cytokinesis begins

27. Cytokinesis Animal Cells: –Form Cleavage Furrow –membrane pinches off and half of the cell contents go to each new daughter cell Plant Cells: –forms Cell Plate –because plants have a rigid cell wall, the plasma membrane does not pinch in; a cell plate forms across the equator

28. When do cells divide? Growth of a multicellular organism - due to increase in # of cells, not size of cells! –Living things grow by producing more cells, not cells getting bigger same size now as baby, size or organism depends on number of cells –Cell division enables multicellular organisims to grow and develop from a single fertilized egg – one single cell can divide to form a multicellular human –Cells can grow a little bit ex fat cells don’t divide once reach puberty –but can grow much larger - even if not growing in size still produce new cells to replace old Cell division even when fully grown to renew and repair cells or replace old that die of wear and tear or accidents ex bone marrow supplys new blood cells *Red blood cells only live 120 days 2.5 million new must be made/second?, but must be controlled growth (or cancer) * Cells that line the digestive system organs – go through entire cell cycle in 6 hours