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Understanding Mitosis and Cell Division Process

This text provides an explanation of mitosis and its importance in cell division for both asexual and sexual reproducing organisms. It covers the phases of mitosis, including prophase, metaphase, anaphase, and telophase, and discusses the cell cycle and its regulation. The text also emphasizes the role of checkpoints in ensuring proper cell division.

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Understanding Mitosis and Cell Division Process

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  1. Chapter 2Mitosis and Meiosis Honors Genetics Lemon Bay High School

  2. Chromosomes vs. Chromatids Each sister chromatid was inherited from one parent and contains identical gene sites (loci) along their lengths.

  3. QUESTION • With regard to the homologous chromosomes pictured at right: • How many sister chromatids are present? • How many chromosomes are present? • How many PAIRS of homologous chromosomes are present?

  4. QUESTION • With regard to the homologous chromosomes pictured at right: • How many sister chromatids are present? • 16 • How many chromosomes are present? • 8 • How many PAIRS of homologous chromosomes are present? • 4

  5. MITOSIS = Division of nucleus

  6. 2.3: Purpose of Mitosis • Partitions chromosomes into dividing cells. • Necessary for both Asexual and Sexual reproducing organisms. • Asexual • Unicellular organisms such as protozoans and some fungi • Basis for the production of new organisms. • Sexual • Multicellular organisms begin life as a single fertilized egg = ZYGOTE. • Mitotic activity that follows is the foundation for growth and development of the organism. • Occurs in two phases • Karyokinesis • Interphase, replication of DNA, growth, cell “work”, mitosis • Cytokinesis • Division of cytoplasm and organelles into two new cells.

  7. Cell Cycle/Cell Clock Time spent from end of one cycle (cell life) to the start of next cycle (cell life).

  8. G1 • Birth of new cell • Metabolic activity • Cell growth • Cell differentiation • G0 = Quiescence • Metabolic activity • Non-proliferative = will not undergo mitosis • S = Synthesis • Replication of DNA • G2 • Metabolic activity • Cell growth • Cell differentiation • Volume of cell has roughly doubled • M = Mitosis • No Metabolic activity • No cell growth • Occurs in 4 steps • Prophase • Metaphase • Anaphase • Telophase

  9. What determines Quiescence? The Type of Cell • Labile • Stabile • Permanent

  10. Prophase • Over one half of mitosis is spent in Prophase • Centriole • Migrates to opposite poles of the cell • Forms spindle fibers from centriole to centriole • Breakdown of nuclear envelope • Chromatin condenses to form chromosomes made of chromatids (the duplication of a single chromosome).

  11. Pro-Metaphase • Chromosome movement toward the equator of the cell. • Kinetochore is the joining of the spindle fiber to the centromere. Improper connection can result in devastating results for the resulting cell. Metaphase • Chromosomes are aligned along the midline of the cell, what is called the metaphase plate.

  12. Anaphase • Critical phase of chromosome distribution • The shortest phase of mitosis • Sister chromatids of each chromosome disjoin and migrate to opposite poles. • For complete disjunction, each centromere MUST split in 2. • Molecular motors PULL the new daughter chromosomes to opposite pulls with help of the spindle fibers.

  13. Telophase and Cytokinesis • Final stage of Mitosis • As cells pull apart cell membrane and cytoplasmic structures, a cell furrow appears. This is where the cell pinches to begin formation of 2 new cells • New nuclear membranes begin to form around the daughter chromosomes. • Spindle fibers disappear • Cell enters Interphase.

  14. Text reading • Section 2.3 Mitosis • Pay special attention to Cell-Cycle Regulation and Checkpoints. • Class Text page 22 - 26 • Online Text page 23 - 28

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