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Lesson Overview

Lesson Overview. 10.2 The Process of Cell Division. Chromosomes. Chromosomes make it possible to separate DNA precisely during cell division. The genetic information that is passed on from one generation of cells to the next is carried by chromosomes.

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Lesson Overview

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  1. Lesson Overview 10.2 The Process of Cell Division

  2. Chromosomes • Chromosomes make it possible to separate DNA precisely during cell division. • The genetic information that is passed on from one generation of cells to the next is carried by chromosomes. • Every cell must copy its genetic information before cell division begins. • Each daughter cell gets its own copy of that genetic information. • Cells of every organism have a specific number of chromosomes. • mitosis

  3. Prokaryotic Chromosomes • Prokaryotic cells lack nuclei. Instead, their DNA molecules are found in the cytoplasm. • Most prokaryotes contain a single, circular DNA molecule, or chromosome, that contains most of the cell’s genetic information. • DNA unzips making 2 strands and each strand is copied giving 2 identical copies of DNA.

  4. Binary fission • Binary fission- Bacterial cell grows and then splits into equal halves. • Product of binary fission – 2 identical bacterial

  5. Eukaryotic Chromosomes • In eukaryotic cells, chromosomes are located in the nucleus, and are made up of chromatin. • Chromatin is composed of DNA and histone proteins.

  6. DNA coils around histone proteins to form nucleosomes • The nucleosomes interact with one another to form coils and supercoils that make up chromosomes.

  7. The Eukaryotic Cell Cycle • Interphase consists of phases: G1, S, G2 • Interphase is the time between cell divisions. • G1 – rapid cell growth, a cell is in this part • of the cell cycle for the longest period of time • between cell divisions. • S – DNA is copied, chromosome replicated • is now two sister chromatids joined at • centromere

  8. G2 Phase: Preparing for Cell Division • G2 – Organelles replicate, microtubules are • reassembled to form spindle apparatus that • will move chromosomes, cell is now • prepared for mitosis. • This is the shortest phase of interphase. • An eukaryotic cell spends most of its time in • Interphase.

  9. M Phase: Cell Division • In eukaryotes, cell division occurs in two stages: mitosis and cytokinesis. • Mitosis is the division of the cell nucleus. • Cytokinesis is the division of the cytoplasm. • After cytokinesis is complete, the cell will be in Interphase again.

  10. MITOSIS • Biologists divide the events of mitosis into • four phases: • 1. Prophase • 2. Metaphase • 3. Anaphase • 4. Telophase

  11. Chromosomes condense and become visible. Centrioles form and take up positions on opposite ends of the nucleus. Spindle becomes visible. Nuclear membrane breaks down, and the nucleolus disappears. PROPHASE

  12. Metaphase • Spindle fibers (kinetochore) assist in moving the chromosomes to the equator (middle) of the cell. • The centromeres of all the sister chromatids line up. • The imaginary line that bisects each of • the chromatids through the centromere • is called the metaphase plate.

  13. ANAPHASE • Sister chromatids separate from each other at the centromere. • The spindle now pulls each chromosome to opposite ends of the cell (toward the centrioles). • The spindle is taken apart as the chromosomes move. • Each pole now has one complete set of chromosomes.

  14. TELOPHASE • Chromosomes uncoil, spindle fibers disappear, and the nuclear membrane reforms. • Mitosis is complete. • Is the cell divided???

  15. Cytokinesis • Cytokinesis is the division of the cytoplasm. Cytokinesis completes the process of cell division – it splits one cell into two. • Animal cells pinch in the membranes forming a cleavage furrow.

  16. Cytokinesis in Plant Cells • In plants, the cell membrane is not flexible enough to draw inward because of the rigid cell wall. • Instead, a cell plate forms between the divided nuclei that develops into cell membranes. • The plate is formed from secretions of the golgi. • A cell wall then forms in between the two new membranes.

  17. Important Cell Structures Involved in Mitosis • Chromatin- genetic material in a non-dividing cell, loose strands • Chromatid – each strand of a duplicated chromosome • Centromere – the area where each pair of chromatids is joined • Centrioles – tiny structures located in the cytoplasm of animal cells that help organize the spindle • Spindle – a fanlike microtubule structure that helps separate the chromatids

  18. The Stages of the Cell Cycle mitosis review

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