BIO SCI

• Cell cycle


  One "turn" or cycle consisting of interphase, followed by mitosis and cytokinesis
• Interphase


  Period of the cell cycle during which the cell is not dividing
• Mitosis


  Division of genetic material, during which the cell nucleus breaks down and two new, fully functional, nuclei are formed
• Cytokinesis


  Divides the cytoplasm into two distinctive cells
• Cell cycle


  1. Interphase

  2. Mitosis

  3. Cytokinesis
• G1 phase


  First gap, or growth phase in the cell cycle
• S phase


  Period during which a cell replicates its DNA
• G2 phase


  Second gap phase, during which the cell continues to grow and makes the necessary preparations for mitosis
• G0 phase


  Resting phase of the cell cycle
• Interphase


  1. G1 phase

  2. S phase

  3. G2 phase
• Cells in G0 phase have temporarily or permanently stopped dividing
• Sister chromatids


  Copies of a chromosome produced by DNA replication, physically bound together by a centromere
• Homologous pair of chromosomes

  Two paired chromosomes which were inherited separately, one from each parent
• Mitosis


  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase
• Prophase


  • Chromatin coils and condenses into visible chromosomes
  • Nuclear envelope disintegrates
  • Centrosomes move apart and microtubules form mitotic spindle
• Metaphase


  • Sister chromatids line up along the metaphase plate
• Anaphase


  • Sister chromatids are pulled to opposite poles of the cell
• Telophase


  • New daughter nuclei form, chromosomes uncoil, mitotic spindle breaks apart
• Cleavage furrow


  Contractile band of microfilaments that forms around the midline of the cell during cytokinesis
• Cells that complete mitosis but fail cytokinesis result in larger cells with more than one nucleus
• Meiosis


  Cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells
• Meiosis I


  1. Prophase I

  2. Prometaphase I

  3. Metaphase I

  4. Anaphase I

  5. Telophase I and Cytokinesis I
• Meiosis II


  1. Telophase II

  2. Cytokinesis II
• Meiosis I


  • Homologous chromosomes separate
  • Crossing over increases genetic diversity
• Meiosis II


  • Sister chromatids separate, producing 4 genetically unique haploid gametes
• Mitosis


  Produces identical daughter cells
• Meiosis


  Produces genetically unique haploid gametes
• Gametogenesis


  Process of forming gametes (sperm or eggs) from diploid cells
• Spermatogenesis


  Process of forming sperm cells by meiosis in testes
• Oogenesis


  Process of forming eggs by meiosis in ovaries
• Human males produce 200,000,000 sperm per day, while females produce one egg per menstrual cycle