The Cell Cycle and Cellular Reproduction

1. The Cell Cycle and Cellular Reproduction Mader: Biology 8th Ed.

2. CELL DIVISION 1. WHAT IS THE SEQUENCE OF EVENTS IN THE CELL CYCLE? 2. WHAT ARE THE DIFFERENCES IN CELL DIVISION BETWEEN PROKARYOTES AND EUKARYOTES? Mader: Biology 8th Ed.

3. MITOSIS • SIMPLE CELL DIVISION • CREATES TWO GENETICALLY IDENTICAL DAUGHTER CELLS • TO GROW, REPAIR, REPLACE AND IN SIMPLE ORGANISMS REPRODUCE • CANCER OCCURS WHEN THE ENZYME REGULATING THE CELL CYCLE GOES AWRY Mader: Biology 8th Ed.

4. Interphase • Most of the cell cycle is spent in interphase. • G1 - Cell doubles its organelles and accumulates materials needed for DNA synthesis. • S - DNA replication. • G2 - Cell synthesizes proteins necessary for cell division. Mader: Biology 8th Ed.

5. Mitotic Stage • Cell division stage that includes mitosis (nuclear division) and cytokinesis (cytoplasm division). Mader: Biology 8th Ed.

6. Cell Cycle Mader: Biology 8th Ed.

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12. Cell Cycle Control • Researchers have identified internal signal protein (cyclin) that increases and decreases as cell cycle continues. • Must be present for the cell to proceed from the G2 stage to the M stage and from G1 stage to S stage. • Allows time for any damage to be repaired. Mader: Biology 8th Ed.

13. Cell Cycle Control Mader: Biology 8th Ed.

14. Apoptosis • Often defined as programmed cell death. • Cells routinely harbor enzymes (caspases) necessary for apoptosis to occur. • Ordinarily held in check by inhibitors, but can be unleashed by internal or external signals. • Mitosis increases and apoptosis decreases the number of somatic cells. Mader: Biology 8th Ed.

15. Apoptosis Mader: Biology 8th Ed.

16. Prokaryotic Cell Division • Asexual Reproduction - offspring are genetically identical to the parent. • Binary fission produces two (binary) daughter cells that are identical to the original parent. • Prokaryotes contain a single chromosome with only a few proteins. Mader: Biology 8th Ed.

17. Binary Fission Mader: Biology 8th Ed.

18. Mitosis • When a eukaryotic cell is not undergoing division, the DNA within the nucleus is a tangled mass of chromatin. • Condenses into chromosomes • Each species has a characteristic number of chromosomes. • Diploid (2n) - Two of each kind. • Haploid (1n) - One of each kind. Mader: Biology 8th Ed.

19. Mitosis • During mitosis, a diploid nucleus divides to produce diploid daughter nuclei. • Two identical chromatids are called sister chromatids. • Attached to each other at centromere. • During nuclear division, sister chromatids separate at the centromeres, and each duplicated chromosome gives rise to two daughter chromosomes. Mader: Biology 8th Ed.

20. Duplicated Chromosomes Mader: Biology 8th Ed.

21. Mitosis in Animal Cells • Each centrosome in an animal cell contains a pair of barrel-shaped organelles (centrioles) and an array of short microtubules (aster). • Centrsomes organize mitotic spindle, which contains many fibers, each composed of a microtubule bundle. Mader: Biology 8th Ed.

22. Table 9.1 Mader: Biology 8th Ed.

23. Mitosis in Animal Cells • Prophase • Chromatin has condensed. • Nucleolus disappears. • Nuclear envelope disintegrates. • Spindle begins to assemble. • Kinetochores develop on centromere. • Attach sister chromatids to spindle fibers. Mader: Biology 8th Ed.

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28. Mitosis in Animal Cells • Metaphase • Chromosomes, attached to kinetochore fibers, are in alignment at center of cell. Mader: Biology 8th Ed.

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31. Mitosis in Animal Cells • Anaphase • Sister chromatids split, producing daughter chromosomes. • Daughter chromosomes are pulled to opposite poles. Mader: Biology 8th Ed.

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34. Mitosis in Animal Cells • Telophase • Spindle disappears as new nuclear envelopes form around the daughter chromosomes. • Chromosomes become diffuse chromatin again. • Nucleolus appears in each daughter nucleus. Mader: Biology 8th Ed.

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37. Cytokinesis • Cytokinesis accompanies mitosis in most cells, but not all. • Mitosis without cytokinesis results in a multinucleated cell. • Begins in anaphase, continues in telophase, but does not reach completion until the following interphase begins. Mader: Biology 8th Ed.

38. Cytokinesis • Animal Cells • Cleavage furrow, membrane indentation between daughter nuclei, begins as anaphase nears completion. • Deepens when a band of actin filaments (contractile ring) forms a circular constriction between the two daughter cells. Mader: Biology 8th Ed.

39. Cytokinesis in Animal Cells Mader: Biology 8th Ed.

40. Plant Cell Division • Meristematic plant tissue retains the ability to divide throughout the plant’s life. • Found at root and shoot tips. Mader: Biology 8th Ed.

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45. Cytokinesis • Cytokinesis accompanies mitosis in most cells, but not all. • Mitosis without cytokinesis results in a multinucleated cell. • Begins in anaphase, continues in telophase, but does not reach completion until the following interphase begins. Mader: Biology 8th Ed.

46. Cytokinesis • Plant Cells • Rigid cell wall surrounding plant cells does not permit cytokinesis by furrowing. • Begins with formation of a cell plate which eventually becomes new plasma membrane between the daughter cells. Mader: Biology 8th Ed.

47. Cytokinesis in Plant Cells Mader: Biology 8th Ed.

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49. The Cell Cycle and Cancer • Cancer is a growth disorder that results from the mutation of genes regulating the cell cycle. • Carcinogenesis, development of cancer, tends to be gradual. Mader: Biology 8th Ed.

50. Characteristics of Cancer Cells • Lack differentiation. • Have abnormal nuclei. • Form tumors. • Loss of contact inhibition. • Undergo metastasis. • New tumors distant from primary tumor. • Undergo angiogenesis. • Formation of new blood vessels. Mader: Biology 8th Ed.