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Cell Division

Cell Division. Cellular Reproduction. Organism’s life begins as one cell Rudolf Virchow (1858) stated: All cells come from cells Prokaryotes divide only to reproduce Asexual repro: 1 parent  2 daughters AKA Binary fission (“dividing in half”) One set of DNA duplicates, cell divides.

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Cell Division

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  1. Cell Division

  2. Cellular Reproduction • Organism’s life begins as one cell • Rudolf Virchow (1858) stated: All cells come from cells • Prokaryotes divide only to reproduce • Asexual repro: 1 parent  2 daughters • AKA Binary fission (“dividing in half”) • One set of DNA duplicates, cell divides

  3. Important Definitions • DNA: a molecule composed of deoxyribose nucleotides and contains the genetic information of living cells • Chromosome: a single DNA double helix together with proteins that help to organize the DNA • Chromatid: one of the two identical strands of DNA and protein that forms a replicated chromosome • Gene: a unit of heredity; specifies the amino acid sequence of proteins and hence particular traits • Allele: one of several alternative forms of a particular gene • Locus: the physical location of a gene on a chromosome

  4. Important Definitions (cont.) • Diploid: referring to a cell with pairs of homologous chromosomes • Haploid: referring to a cell that has only one member of each pair of homologous chromosomes • Homologous Pair: two homologues that are similar in appearance and genetic information that pair during meiosis • Heterozygous: carrying two different alleles of a given gene • Homozygous: carrying two copies of the same allele of a given gene

  5. What Are Mitosis And Meiosis? • Both are types of reproduction used during the cell cycle • Each type of cell division are specialized for different types of cells • Both undergo the cell cycle in very similar, yet very different ways

  6. Mitosis • Mitosis is the division of chromosomes in a cell • Usually followed by cytokinesis or cell division • Daughter cells produced after mitosis have same number of chromosomes as original cell • Purpose of mitosis is replication of somatic cells and asexual reproduction • Somatic cells include all cells in the body except the egg or sperm

  7. Meiosis • Meiosis is the division and reduction of the chromosomes of a cell • Daughter cells produced have half the chromosomes as the original cell • Purpose of meiosis is the production of gametes (sex cells)

  8. Interphase And Synthesis Stages Of Mitosis And Meosis • During Interphase the cell carries out normal activities such as metabolism and protein synthesis • During synthesis the DNA in each chromosome is replicated (GUEST, 2009)

  9. Eukaryotic cells divide for reproduction, growth, and replacement of cells • Other organisms (plants & animals especially) reproduce through sexual reproduction • Sperm + Egg  offspring • Offspring gets two sets of genetic information, one from each parent

  10. The Chromosome • DNA is contained in structures called chromosomes within the nucleus of the cell • “chroma” color, “soma” body • Most of the time, chromatin fills the nucleus • Tangled mass of fibers of DNA & protein • When a cell begins to divide, the chromatin condenses and coils into chromosomes • Each chromosome has one long DNA molecule containing thousands of genes

  11. The Chromosome • Before a cell divides, it must duplicate its chromosomes • DNA replication! • Once duplicated, the chromosomes have sister chromatids with identical genes, joined at a centromere • When the cell divides, half goes to each daughter cell

  12. The Cell Cycle • Sequence of events from the time a cell divides to when it forms two daughter cells • Serves to double the cell’s parts, then splits • Stages: • Interphase 90% • Mitotic phase 10% (SMITH, 2010)

  13. Mitotic Phase • Unique to eukaryotes • Ends with 2 identical cells • Sub-stages of Mitosis: • Prophase • Metaphase • Anaphase • Telophase • Cytokenisis

  14. Prophase • Sister chromatids are attached at centromere • Centrioles separate and extend spindle fibers • Nucleolus disappears and nuclear envelope breaks down • Kinetochores form on each chromatid, spindle fibers attach

  15. Metaphase • Centrosomes at poles • Chromosomes lined up at metaphase plate (cell’s equator) • Kinetochores of sister chromatids face opposite poles

  16. Prophase And Metaphase Stages of Mitosis • The prophase stage • chromosomes condense and would be visible under a light microscope • the nuclear membrane degrades • In the metaphase stage the chromosomes line up along the equator (PATTERSON, 2008)

  17. Bibliography GUEST. (2009). MITOSIS. MITOSIS. CHICAGO: SHARESLIDES. TAMARITA. (2008). MITOSIS FINAL. MITOSIS FINAL. NEW YORK: SHARESLIDES. JACKSON. (2010). BIOLOGY MITOSIS. BIOLOGY MITOSIS. LONDON: SHARESLIDES. MARGLEMA. BIOLOGY MITOSIS INTERACTION. BIOLOGY MITOSIS INTERACTION. NEW YORK: SHARESLIDES. PATTERSON, C. (2008). THE CELL CYCLE. AN OVERVIEW OF THE CELL CYCLE. BOSTON: SHARESLIDES. SMITH. (2010). BIOLOGY-MITOSIS. BIOLOGY MITOSIS. LONDON: SHARESLIDES.

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