Survey
* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project
Download File
Document related concepts
Transcript
Three reasons why cells reproduce by asexual reproduction: 1. Growth 2. Repair 3. Replacement Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun. Cell that reproduce by asexual reproduction reproduce constantly. Animated Mitosis Cycle http://www.cellsalive.com/mitosis.htm • Interphase • Prophase • Metaphase • Anaphase • Telophase & Cytokinesis Interphase occurs before mitosis begins • Cell is doing all other activities (growth, specilalized functions) • Chromosomes (we have 46 of them) appear as threadlike coils (chromatin) at the start, the chromatin is copied (duplicated – so there are 92) to prepare for cell division • Other organelles are also copied • Centrioles are copied Centrioles Nucleus CELL MEMBRANE Cytoplasm Interphase Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Prophase • Chromatin thickens/condenses into chromosomes • Each chromosome (because it was copied already) consists of 2 identical stands called sister chromatid • These are held together by a centrometre • The nuclear membrane dissolves • Centrioles (or poles) begin to move to opposite end of the cell. • Spindle fibers form between the poles. Centrioles Sister chromatids Spindle fibers Prophase Animal Cell Plant Cell Spindle fibers Centrioles Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Metaphase • Chromatids (or pairs of chromosomes) attach to the spindle fibers. • Chromosomes line up in the middle plane of the cell Centrioles Spindle fibers Metaphase Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Anaphase • Chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell by being pulled by the spindle fibers contracting to the centrioles • The split sister chromatids are called daughter chromosomes Centrioles Spindle fibers Anaphase Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Telophase • Two new nuclei (nuclear membranes) form around the daughter chromosomes. • Chromosomes appear as chromatin (threads rather than rods). • Mitosis ends. Nuclei Chromatin Nuclei Telophase Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Cytokinesis occurs after mitosis • Cell membrane moves inward (is pinched) to create two daughter cells – each with its own nucleus with identical chromosomes in an animal cell • In a plant cell, a new cell wall forms and divides into two daughter cells. Animal Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase Interphase Plant Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase Interphase Cell Cycle 16
