What is Mitosis? (Cell Division) The Cell Cycle and Mitosis

Transcription

1 What is Mitosis? (Cell Division) The Cell Cycle and Mitosis 1. Mitosis: Asexual process where one cell (parent cell) splits into two identical daughter cells that each have a full set of chromosomes For example, 1 human skin cell with 46 chromosomes divides into 2 skin cells with 46 chromosomes each Cell Division 2. Continuous process = happens non-stop for the entire life of the organism (except in certain cells, like nerves) 3. Daughter cells have same function, structure, and chromosomes number as parent cell (unless something goes wrong such as a mutation, which is a change in DNA). Important Vocabulary Words Chromosomes- organized, coiled piece of DNA containing an organismsʼ genes can see them in individual cells during most of the cellʼs life cycle chromosomes exits as stringy chromatin that is wrapped around histone proteins

2 Vocabulary Cont Centromere- Button that holds the sister chromatids together. Centrioles- small, dark, cylindrical structure that aid in celll division. (only found in animal cells) Vocabulary Words Karotypes- a speciesʼ chromosomes map Is used to identify potential problems. Why do cells divide? 1. Replace worn or damaged cells (except nerve cells) 2. Growth/development 3. Cells need to stay small (so they can be efficient in importing / exporting, and maintaining homeostasis) 4. Asexual Reproduction

3 The Cell Cycle All cells time their division using the Cell Cycle The cell cycle is the sequence of growth and division of a cell. Interphase Mitosis - PMAT Prophase Metaphase Anaphase Telophase The Cell Cycle The Cell Cycle Interphase, is where the cell spends the majority of itʼs life. Interphase It is the busiest phase of the cell cycle and is divided into 3 parts (G1, S, and G2). DNA synthesis and replication Rapid growth and metabolic activity Centrioles replicate; cell prepares for division

4 The Cell Cycle Mitosis begins after interphase is finished Prophase: The first phase of mitosis During prophase, the chromatin coils to form visible chromosomes. Spindle fibers Disappearing nuclear envelope Mitosis Doubled chromosome Prophase: The first phase of mitosis The two halves of the doubled structure are called sister chromatids. Prophase: The first phase of mitosis Sister chromatids are held together by a structure called a centromere, which plays a role in chromosome movement during mitosis. Sister chromatids Centromere Centromere is like a BUTTON that holds the chromatids together

5 Metaphase: The second stage of mitosis During metaphase, the chromosomes move to the equator of the spindle. Centromere Anaphase: The third phase of mitosis During anaphase, the centromeres split and the sister chromatids are pulled apart to opposite poles of the cell. Sister chromatids Telophase: The fourth phase of mitosis During telophase, two distinct daughter cells are formed. The cells separate as the cell cycle starts over, with the next interphase. Nuclear envelope reappears Cytokinesis Following telophase, the cellʼs cytoplasm divides in a process called cytokinesis. Cytokinesis differs between plants and animals. In animal cells: the plasma membrane pinches in along the equator, forming a cleavage furrow. Two daughter cells are formed

6 Cytokinesis In plant cells: Thereʼs a tough cell wall, so the plasma membrane does not pinch in. A structure known as the cell plate is laid down across the cellʼs equator. A cell membrane forms around each cell, and new cell walls form on each side of the cell plate until separation is complete. Results of Mitosis When mitosis is complete Unicellular organisms remain as single cells. Multicellular organisms, cell growth and reproduction result in groups of cells that work together as tissue to perform a specific function. Results of Mitosis Tissues organize in various combinations to form organs that perform more complex roles within the organism. Multiple organs that work together form an organ system. What characteristic of life is this an example of??

7 Factors Effecting Cell Cycle Rate 1. Available Nutrients 2. Temperature 3. ph 4. Drugs and Chemotheraphy Question 1 The stringy structures in the cell nucleus that contain DNA are. A. centromeres B. chromosomes C. genes D. chlorophylls The answer is B. Chromosomes are the carriers of the genetic material of the cell. A gene is a segment of DNA that controls the production of a protein. Question 2 Look at the diagram and identify the stage of mitosis that is depicted. Centromere Sister chromatids A. prophase B. metaphase C. anaphase D. telophase

8 The answer is B. Metaphase is the short second phase of mitosis, during which the chromosomes begin to line up on the equator of the spindle. Question 3 What is the process by which a cell's cytoplasm divides? A. cytokinesis B. telekinesis C. meiosis D. mitosis The answer is A. Cytokinesis follows telophase and allows the two new cells to separate. Question 4 In multicellular organisms, groups of cells that work together to perform a specific function are called. A. organ systems B. organs C. tissues D. cell cycles

9 The answer is C. Tissues organize to form organs, which work with other organs to form organ systems.