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Cellular Basis of Inheritance

Cellular Basis of Inheritance

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Cellular Basis of Inheritance

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  1. Cellular Basis of Inheritance Chapter 9

  2. Cells come from other cells • Repair • Growth • Reproduction • Asexual Reproduction • Sexual Reproduction

  3. Sexual Reproduction • Genetic Material comes from 2 parents

  4. Asexual Reproduction • Genetic Material comes from 1 parent • Budding • Cloning • Fragmentation • Sporulation

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

  6. 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

  7. 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

  8. 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)

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

  10. 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

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

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

  13. 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

  14. 1 chromosome 1 chromatid 1 chromosome (doubled) 2 chromatids (sisterchromatids) Replication Chromosome or chromatid?

  15. Mitosis and Meiosis How and Why Cells Divide

  16. Onion root

  17. Interphase • G1 phase= Growth phase • S phase = synthesis phase – make copy of DNA • G2 phase – Growth and cell maintenance for preparation of division occurs: - for example copying organelles

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

  19. Prophase • Chromatin coils up into visible chromosomes

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

  21. Prophase • Spindle fibers – form between centrioles - And attach to chromosomes

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

  23. 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)

  24. 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)

  25. End of Mitosis • Nuclei go back into interphase • Cytokinesis begins

  26. 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

  27. 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