LESSON 4 BIO

• Binary fission


  The process by which prokaryotes produce new individuals that are genetically identical to the parent organism

  
• Cell division


  The process in which one cell, called the parent cell, divides to form two new cells, referred to as daughter cells

  
• Types of cell division


  • Mitosis (in somatic cells)
  • Meiosis (for gamete production)
• Mitosis


  • Occurs in somatic cells (body cells)
  • Results in two genetically identical daughter cells
• Meiosis


  • Occurs for the production of gametes in sexual reproduction
• In both mitosis and meiosis, the nucleus divides and may end in cytokinesis
• Importance of cell division in human development

  • Cells divide at different rates
  • Some tissues require frequent renewing (e.g. lining of stomach replaced every 5 days)
  • Other tissues divide less frequently (e.g. bones and connective tissues in adults)
  • Skin cells shed off and are replenished daily
  • Red blood cells replaced every 120 days
  • Wound and sunburn skin heal
  • Nails and hair become longer
• Nucleus


  The control center of the cell that contains DNA
• DNA (deoxyribonucleic acid)


  A double-stranded nucleic acid that is tightly coiled around proteins called histones, to form chromosomes
• Nucleotide


  The basic building block of the nucleic acids DNA and RNA, made up of a nitrogen-containing base, a phosphate group, and a sugar molecule
• DNA replication


  1. Produces two identical copies of a DNA molecule

  2. Essential for cell division during growth or repair of damaged tissues

  3. Ensures each new cell receives its own copy of the DNA

  
• Centriole


  A small cylindrical structure in the cytoplasm in most eukaryotes, that assists in cell division by forming spindle fibers and aster rays
• Cell cycle


  An orderly set of events that culminates in the production of new cells
• Phases of the cell cycle


  • Interphase (G1, S, G2)
  • M phase (Mitosis or Meiosis)
• Interphase


  1. G1 phase (cell growth and organelle formation)

  2. S phase (DNA replication)

  3. G2 phase (cell growth and protein synthesis)
• Mitosis


  1. Prophase (chromosomes thicken and coil, nuclear membrane disintegrates)

  2. Metaphase (chromosomes align at the center)

  3. Anaphase (sister chromatids separate and move to opposite poles)

  4. Telophase (nuclear membrane reforms, spindle fibers dissolve, cytoplasm divides)
• Cell cycle checkpoints


  Groups of proteins that check the condition of cells and determine if they are ready to proceed to the next stage of the cell cycle
• Types of cell cycle checkpoints


  • G1 checkpoint (ensures cell is ready for DNA synthesis)
  • G2 checkpoint (ensures cell is mature enough to divide)
  • M checkpoint (ensures cell is ready to complete cell division)
• If cell cycle checkpoints are not functioning properly, it may result in unregulated cell division and cancer
• Cyclin dependent kinase


  A group of proteins that control the progression of the cell cycle by activating particular enzymes
• Tumor protein (p53)


  A protein that blocks the cell cycle if the DNA is damaged
• Cancer


  Occurs when cells undergo mutation, resulting in their inability to control their normal growth mechanisms and leading to unregulated cell division
• Tumor


  A solid mass of cancer cells that are formed from rapid cell division
• Types of tumors


  • Malignant (cancerous)
  • Benign (non-cancerous)
• Metastasis


  The spreading of cancerous cells to other parts of the body
• Carcinogen


  Something that can cause cancer, such as a substance in the air, a product, or a chemical in foods and drinks
• Eating the right foods and filling your body with the minerals and nutrients it needs can help reduce your chances of developing certain types of cancer