Transcript Mitosis
CELL CYCLE The Cell Cycle • Cells must divide to maintain maximum efficiency. • Mitosis is the process in which somatic (body) cells divide to form a new cell. • Mitosis consists of four phases. • Interphase is the period in between each mitotic cell division. Reproduction • Asexual Reproduction: A single cell or group of cells each duplicates its genetic material and then splits into two new genetically identical cells. – The offspring are genetically identical • Sexual Reproduction: Genetic material from each of two parents combines, producing offspring that differ genetically from either parent. – Involves the union of sex cells (egg and sperm) Parent cell DNA replicates Cell division = One cell makes two cells Two daughter cells are genetically identical to each other and to parent cell = clones The same DNA can appear in two forms Chromatin = uncondensed DNA Chromosome = condensed DNA 1 Chromosome 1 chromatid per chromosome 1 DNA double helix DNA replication 1 Chromosome 2 chromatids per chromosome 2 DNA double helices Cell division in eukaryotic cells: Cytokinesis = division of the cytoplasm Interphase • Interphase is made of 3 stages. • The Gap 1 and 2 or G1 and G2 phase is when cells grow and make RNA, proteins, and other macromolecules. • The S or Synthesis phase is when the cell is making DNA. DNA Replication • During the S phase of the cell cycle, DNA replicates. • A short section of the DNA uncoils. • New nucleotides bond to the open sections of the DNA. • The “new” and “old” sections of DNA separate and now there are 2 DNA strands. Interphase • • • • • • • ATP is synthesized. Damaged parts are repaired. Wastes are excreted. Proteins are made. Organelles are formed. Chromosomes are copied. Specialized tasks are performed . Interphase nucleus DNA = Chromatin Interphase Chromatin in nucleus Mitosis • • • • • Mitosis consists of four phases Prophase Metaphase Anaphase Telophase Prophase • • • • • Longest phase. Chromatin coils. Nucleus disappears. Centrioles migrate. Spindle forms. Prophase Nuclear membrane disappears Nucleolus disappears Chromatin condenses into chromosomes Spindle fibers appear Chromatin Chromosomes Metaphase • • Chromatids attach to spindle fibers. Chromatids migrate to equator of spindle. Metaphase Chromosomes line up in center of cell Centromere = holds chromatids together Chromatids (DNA double helix) Two chromatids per chromosome Anaphase • • • Centromere splits. Chromatids are separated. Chromatids are now called chromosomes. Anaphase = Sister chromatids separate from each other Telophase • • • Cytoplasm divides. Nucleus reappears. Chromosomes uncoil. Telophase Cytokinesis makes 2 new cells Chromosomes decondense into chromatin Nucleolus reappears Nuclear membrane reappears Early Telophase Late Telophase Cytokinesis • In the process called cytokinesis, the cytoplasm divides and two identical daughter cells are formed. Animal cell membranes pinches together between two new cells Cytokinesis Plant cell wall grows between two new cells Interphase Prophase Prophase Telophase Metaphase Telophase Anaphase Plant Cytokinesis = division of cytoplasm Telophase Interphase Anaphase Prophase Animal cytokinesis = pinching of plasma membrane Early telophase http://www.unm.edu/~asmund/mitosis.jpg Metaphase Late Telophase Plant or Animal cell mitosis? Plant