WEEK 7

• 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
• 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
• During interphase, each cell contains two copies of each chromosome
• A human cell has 46 chromosomes, so during interphase there are 92 chromatids (46 x 2) in the cell
• 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
  • Nucleolus disappears
  • Centrosomes move apart and microtubules extend
• Metaphase

  • Sister chromatids line up along the metaphase plate
• Anaphase

  • Sister chromatids separate and are pulled to opposite poles
• Telophase

  • New daughter nuclei form
  • Chromosomes uncoil
  • Nucleoli reappear
  • Mitotic spindle breaks apart
• Cleavage furrow

  Contractile band that forms around the midline of the cell during cytokinesis
• Cytokinesis divides the cytoplasm and cell body into two new cells
• Meiosis

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

  • Homologous chromosomes are separated into two cells
  • Crossing over occurs to increase genetic diversity
• 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
• Mitosis produces two identical daughter cells, while meiosis produces four genetically unique gamete cells
• Gametogenesis

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

  Process of forming sperm cells by meiosis in the testes
• Oogenesis

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