MITOSIS

Cell Reproduction All cells come from pre-existing cells All cells come from pre-existing cells Cell division results in two identical cells Cell division results in two identical cells

Terms to Know Chromatin: long strands of DNA found in the nucleus when a cell is not dividing Chromatin: long strands of DNA found in the nucleus when a cell is not dividing Chromosomes: dark staining structures that contain DNA and appear during nuclear division Chromosomes: dark staining structures that contain DNA and appear during nuclear division Chromatids: identical halves of a duplicated chromosome formed during the first stage of mitosis Chromatids: identical halves of a duplicated chromosome formed during the first stage of mitosis

The Cell Cycle The sequence of growth,development, and division of a cell The sequence of growth,development, and division of a cell There are five stages There are five stages –Interphase –Prophase –Metaphase –Anaphase –Telophase

Interphase Phase that a cell spends a majority of its life- span Phase that a cell spends a majority of its life- span Growth phase Growth phase Chromosomes are duplicated here Chromosomes are duplicated here Precedes mitosis Precedes mitosis –Mitosis: period of nuclear division

Interphase Divided into three parts (Fig.8.10) Divided into three parts (Fig.8.10) –G1: protein synthesis is high as cell grows –S Stage: chromosomes are replicated and divide to form sister chromatids –G2: chromosomes coil, proteins are being synthesized as cell prepares for mitosis Cell Cycle Cell Cycle

Prophase First and longest mitotic stage First and longest mitotic stage Chromatin coils into more dense chromosomes Chromatin coils into more dense chromosomes Sister chromatids are formed and held together by a centromere Sister chromatids are formed and held together by a centromere

Prophase Nuclear envelope begins to disappear Nuclear envelope begins to disappear Centrioles (structures made of microtubules) begin to migrate to opposite ends of the cell Centrioles (structures made of microtubules) begin to migrate to opposite ends of the cell Spindle fibers form between the centrioles Spindle fibers form between the centrioles

Metaphase Short, second phase Short, second phase Chromosomes attach to spindle fibers Chromosomes attach to spindle fibers Chromosomes line up on the midline of the spindle Chromosomes line up on the midline of the spindle

Anaphase Third phase Third phase Centromeres split Centromeres split Chromatids separate Chromatids separate Chromatids are pulled apart by spindle fibers Chromatids are pulled apart by spindle fibers

Telophase Final phase Final phase Chromatids reach opposite sides of the cell Chromatids reach opposite sides of the cell Chromosomes unwind Chromosomes unwind Spindle disappears Spindle disappears Nuclear envelope reappears Nuclear envelope reappears

Cytokinesis Animal Cells Plasma membrane pinches Plasma membrane pinches cleavage furrow forms cleavage furrow forms Cytoplasm is divided Cytoplasm is divided

Cytokinesis Plant Cells Cytoplasm does not pinch Cytoplasm does not pinch Cell plate forms across equator Cell plate forms across equator Cell membrane forms around each new cell Cell membrane forms around each new cell Cell wall forms on each side of the cell plate Cell wall forms on each side of the cell plate

Review Questions What is the longest phase of the cell cycle? What is the longest phase of the cell cycle? Which cells divide using mitosis and how many cells are produced at the end of the process? Which cells divide using mitosis and how many cells are produced at the end of the process? List the phases of Mitosis in order and state one identifying characteristic of each. List the phases of Mitosis in order and state one identifying characteristic of each. At what point in the cell cycle does DNA replication occur? At what point in the cell cycle does DNA replication occur? Do daughter cells have identical DNA to the parent cell after the process of Mitosis? Do daughter cells have identical DNA to the parent cell after the process of Mitosis? Describe two differences between a plant and animal cell in the process of Mitosis. Describe two differences between a plant and animal cell in the process of Mitosis.

Abnormal Cell Cycle: Cancer Cancer Cancer –Uncontrolled growth and division of cells –Failure in regulation of the cell cycle –Crowds out normal cells; leading to loss of tissue function

Causes of Cancer Changes (mutations) on segments of DNA Changes (mutations) on segments of DNA Genetic Risk Genetic Risk Environmental and behavioral risk factors Environmental and behavioral risk factors Environmental and behavioral risk factors Environmental and behavioral risk factors –Carcinogens (may cause cancer or increase risk)  Consumer products  Industry  Chemicals  Ultraviolet radiation

Apoptosis Controlled programmed cell death Controlled programmed cell death Living Examples: Living Examples: –spaces between fingers and toes –Cells that are damaged beyond repair

Applying our Knowledge of Cell Division Cells usually have a specific function Cells usually have a specific function Stem Cells are unspecialized cells that can develop into specialized cells under the right conditions Stem Cells are unspecialized cells that can develop into specialized cells under the right conditions Stem Cell AnimationSeeds of Hope Stem Cell AnimationSeeds of Hope Stem Cells Breakthrough Stem Cells Breakthrough

Two Types of Stem Cells Embryonic Stem Cells After a sperm fertilizes an egg, the resulting mass of cells that has not yet specialized After a sperm fertilizes an egg, the resulting mass of cells that has not yet specialized Controversial because of the source of the cells Controversial because of the source of the cells Adult Stem Cells Found in various tissues in the body Found in various tissues in the body Might be used to repair same type of tissue in which was found. Might be used to repair same type of tissue in which was found. Less controversial because consent is obtained from donors. Less controversial because consent is obtained from donors.