cell cycle

• Mitosis


  A type of nuclear division that produces two new "daughter" nuclei, each containing the same number of chromosomes as the parent nucleus
• Meiosis


  A type of nuclear division that produces four new "daughter" nuclei, each containing half the number of chromosomes as the parent nucleus
• Stages of mitosis


  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase
• Prophase


  • Chromosomes coil up into rod-shaped structures
  • Chromosomes are double-stranded
  • Nucleoli and nuclear membrane disappear
  • Spindle fibers are formed
• Metaphase


  • Rod-shaped double-stranded chromosomes arrange themselves at the equatorial plate
  • Kinetochores attach the chromosomes to the spindle fibers
• Cell cycle


  A repeating series of events, including growth, DNA synthesis, and cell division
• Phases of eukaryotic cell cycle


  • Gap 1 (G1)
  • Synthesis (S)
  • Gap 2 (G2)
  • Mitosis (M)
• Gap 1 (G1)


  Cell grows
• Synthesis (S)


  Cell replicates its DNA
• Gap 2 (G2)


  Cell produces organelles and materials for division
• Mitosis (M)


  Includes both mitosis and cytokinesis, when the nucleus and then the cytoplasm divide
• Chromosome


  Threadlike structures in the nucleus of cells that are made up of molecules of protein and DNA, responsible for the transmission of traits from one generation to the next
• Chromatid


  One of the two identical parts of a chromosome
• Kinetochore


  The point where two chromatids touch
• Haploid cell


  Contains only one set of chromosomes
• Diploid cell


  Contains two sets of chromosomes
• Gametes (sperm and egg) are haploid
• Most body cells (also called somatic cells) are diploid
• Anaphase


  1. Kinetochores divide

  2. Four double-stranded chromosomes become eight single stranded chromosomes

  3. Rod-shaped single-stranded chromosomes migrate to the poles
• Telophase


  1. Chromosomes uncoil

  2. Nucleoli and nuclear membrane reappear

  3. Spindle fibers disappear
• Cytokinesis


  Final stage of mitosis where the cytoplasm splits in two and the cell divides
• Meiosis


  Reduces the chromosome number in half, takes place in plants and animals whenever gametes or sex cells are formed through gametogenesis
• Meiosis


  • A special type of cell division where the cell undergoes two rounds of cell division to produce four daughter cells, each with half the chromosome number as the original parent cell and with a unique set of genetic material as a result of crossing over
• Meiosis I


  1. Prophase I: Homologous chromosomes pair up, exchange of genetic material may occur through crossing over

  2. Metaphase I: Each pair of homologous chromosomes attach to a single spindle fiber

  3. Anaphase I: One double-stranded chromosome in the pair moves to one pole, while the other double-stranded chromosome in the pair moves to the opposite pole

  4. Telophase I: Two nuclei are produced, each containing only half the chromosome number of the original parent cell
• Meiosis II


  1. Similar to mitosis, consists of prophase II, metaphase II, anaphase II, and telophase II

  2. Each double-stranded chromosome attaches to spindle fiber, its centromere splits into two, and the two strands of the chromosome migrate to opposite poles

  3. At the end, four haploid (N) daughter cells are produced