Cell Cycle Basics

• Cell Cycle = a series of steps in which an organisms cells grow and divide to form 2 genetically identical diploid daughter cells

• Human cells have 46 chromosomes

Cell Cycle Timing

• G0 (non-dividing cells) can enter /leave the cell cycle based on environmental signals and cues

• Not all cells divide at the same rate

• How often a cell divides is usually based on how much a cell is “used” or exposed to damaging conditions

• Some cells never go through cell cycle (stay in G0) —> brain cells, lens of eyes, nerves

• Cell cycle takes about 24hrs after leaving G0

Steps of the Cell Cycle

• Interphase

  • G1 - growth

    • Grow and develop

    • Make more VIP molecules and structure

  • Synthesis - DNA synthesis

    • DNA replication only

  • G2 - growth 2

    • Finish growing

    • Make extra organelles

    • Produce extra VIP molecules and structures in preparation for division

• M Phase - split nucleus (PMAT)

  • Prophase

    • Nucleus dissolves

    • DNA condenses, chromosomes are visible

    • Spindle fibers form

  • Metaphase

    • Spindle fibers attach to chromosomes

    • Chromosomes line up on the equatorial plate (AKA middle of the cell)

  • Anaphase

    • Contract spindle fibers to move one set of chromosomes to opposite poles of the cell

  • Telophase

    • Nucleus reforms

    • DNA decondenses (chromosomes uncoil basically)

    • Cell membrane starts pinching in

• Cytokinesis - cell splits in two

• Cytoplasm divides

• Cell membrane pinches in to form two genetically identical daughter cells