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Chapter 8

Cell Reproduction. Chapter 8. Objectives:. Describe the process of cell division. I. Chromosome Structure. What are chromosomes Rod shaped structure made of DNA and proteins. Coiled tightly inside a cell’s nucleus. Consists of two identical halves Chromatid – each half of the chromosome

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Chapter 8

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  1. Cell Reproduction Chapter 8

  2. Objectives: • Describe the process of cell division.

  3. I. Chromosome Structure • What are chromosomes • Rod shaped structure made of DNA and proteins. • Coiled tightly inside a cell’s nucleus. • Consists of two identical halves • Chromatid – each half of the chromosome • Centromere – point of attachment for chromatids. • Chromatin – when DNA uncoils so code can be copied

  4. II. Chromosome Numbers • Each species has specific number of chromosomes • Humans = 46 • Sex chromosomes – chromsomes that determine sex of organism • Can also carry genes for other characteristics • Females have 2 “X chromosomes” • Males have “X and Y chromosome” • Autosomes = all of the other chromosomes • Homologous chromosomes = 2 copies of each autosome

  5. Chromosome Numbers of Various Organisms

  6. D. Karyotype • Photo of the chromosomes in a normal human

  7. E. Diploid and Haploid Cells A. Diploid = cells having two sets of chromosomes (2n) B. Haploid = cells having one set of chromosomes (n) a. sex cells a. sperm = male sex cell b. egg = female sex cell

  8. II. Cell Division in Prokaryotes (no nucleus) A. Binary fission – division of cell into two exact copies

  9. III. Cell division in Eukaryotes (Euks have nucleus) • Mitosis – results in new cells that are identical to the original cell • Asexual reproduction – production of offspring from one parent • Meiosis – occurs during the formation of sex cells • Produces gametes – another name for sex cells

  10. IV. Mitosis • Cell cycle – repeating set of events during the life of a cell • Interphase – time between cell divisions • Mitosis – nucleus divides • Cytokinesis – cell divides

  11. Interphase • Spend most of the cycle • Stage of cell growth and maturity

  12. Prophase • 1st phase • Centrosomes appear • Nucleus disappears • Spindle fibers equally divide chromosomes

  13. Metaphase • Chromosomes line up in the middle

  14. Anaphase • Chromatids separate toward opposite poles

  15. Telophase • Spindle fibers disappear • Nuclear envelope forms around each set of chromosomes

  16. Cytokinesis • Cleavage furrow starts to pinch in and eventually separate the cell

  17. Mitosis animation • http://www.sumanasinc.com/webcontent/animations/content/mitosis.html

  18. V. Control of Cell Division • Proteins regulate the control of cell division • Proteins signal the cell to move on to the next steps of cell division

  19. VI. When Control is Lost = Cancer • Signaling proteins do not function properly • Cells divide uncontrollably = Cancer

  20. VII. Meiosis A. Spermatogenosis – production of mature male gametes B. Oogenesis – production of mature female cells

  21. C. Cells go through mitosis twice

  22. D. Crossing over – when chromatids break apart can combine with other chromatids E. Genetic recombination – new mixture of genetic material that is created from crossing over. F. Independent assortment – random separation of chromosomes

  23. VIII. Sexual reproduction • Production of offspring through Meiosis • Creates offspring that are genetically different from parents • Enables species to adapt to new conditions • Example – if a disease strikes a crop of corn, a few plants may have genetic variations that prevent it from dying. These plants will reproduce creating offspring that are also resistant to the disease.

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