Cell Cycle

• Cell theory

  All living things are made of 1 or more cells
• Multicellular organisms


  • Cells work together as part of body tissue
  • Body tissues work together as part of an organ
  • Organs work together as part of an organ system
• Cell cycle

  Cells can grow in size, but multicellular organisms grow by cells dividing to make more cells
• Cancer


  Cells divide too frequently and are not regulated
• Cancer cells


  • May not communicate with healthy cells
  • May not carry out normal cell functions
  • May not anchor themselves securely like other cells, making them more likely to travel
  • Some can secrete their own growth hormone to divert blood vessels and nutrients
• Genetic factors, exposure to toxins/radiation/UV light can make cells more susceptible to becoming cancerous
• Cell cycle

  Cells are either in interphase (growing, replicating DNA, performing functions) or M phase (mitosis and cytokinesis)
• Cell cycle phases

  • G1 (cell growth), S (DNA synthesis), G2 (cell growth in preparation for mitosis), M (mitosis and cytokinesis)
• Checkpoints


  Points in the cell cycle to check if the cell is growing well, replicating DNA correctly, and ready to divide
• Apoptosis

  Cell self-destructs if it cannot fix issues detected at a checkpoint
• G0 phase


  Resting phase where cells are performing functions but not preparing to divide
• The cell cycle is the process by which cells grow, divide, and reproduce.
• Mitosis produces two genetically identical daughter cells from one parent cell.
• Cell division occurs through mitosis or meiosis.
• Interphase consists of three stages: G1 (gap), S (synthesis), and G2 (gap).
• There are two main types of cell division: mitosis (somatic) and meiosis (gametes).
• In mitotic prophase, chromatin condenses into visible chromosomes, spindle fibers form, and nuclear envelope breaks down.
• During interphase, DNA replicates and proteins synthesize.
• Mitosis involves four stages: prophase, metaphase, anaphase, and telophase.
• Meiosis results in four haploid daughter cells with half the number of chromosomes as the parent cell.
• During interphase, DNA replicates during the S stage.
• Every day our bodies must produce millions of skin cells to replace those lost through normal activity
• Each of these cells must have a complete complement of the genetic material prior to cell division
• Cell division

  1. Cell divides into two identical cells

  2. DNA needs to be replicated so that each daughter cell receives an exact copy
• DNA replication

  1. DNA condenses by wrapping around cores of histone proteins forming nucleosomes

  2. This beads on a string structure is called chromatin

  3. As a cell prepares to divide, chromatin coils up further shortening and condensing the chromosome

  4. The replicated chromosomes are called sister chromatids
• Cell cycle

  1. Interphase (G1, S, G2 phases)

  2. Mitosis
• Interphase

  • G1 phase: all the organelle and cytoplasmic components including the centrioles in animal cells replicate
  • S phase: the DNA replicates
  • G2 phase: all the enzymes needed to aid in the process of cell division are produced
• Most eukaryotic cells spend a great deal of time in interphase and a very short period of time actually dividing