Cell Cycle and Mitosis

• Cell division


  The process by which a parent cell divides into two or more daughter cells, ensuring the continuity of life and the growth and repair of tissues in living organisms
• Cell division

  • All cells are derived from pre-existing cells
  • New cells are produced for growth, to replace damaged or old cells and for the production of sex cells
  • Differs in prokaryotes (bacteria) and eukaryotes (protists, fungi, plants, & animals)

  
• DNA (Deoxyribonucleic acid)


  A molecule that carries the genetic instructions used in the growth, development, functioning, and reproduction of all known living organisms

  
• DNA replication


  The process by which a cell duplicates its DNA to ensure that each daughter cell receives an identical copy of the genetic material during cell division

  
• Chromosome


  A thread-like structure composed of DNA (deoxyribonucleic acid) and proteins, and it carries genetic information

  
• Eukaryotic chromosomes

  • All eukaryotic cells store genetic information in chromosomes
  • Most eukaryotes have between 10 and 50 chromosomes in their body cells
  • Human body cells have 46 chromosomes or 23 pairs

  
• Chromatin


  The complex of DNA and proteins that makes up the genetic material in the nucleus of a eukaryotic cell during the interphase of the cell cycle

  
• Chromatid


  A single DNA strand in a replicated chromosome

  
• Centromere


  Structure in a chromosome that holds together the two chromatids (the daughter strands of a replicated chromosome)

  
• Chromosome


  A condensed and visible structure formed by the coiling and folding of chromatin

  
• Types of cell reproduction

  • Asexual reproduction (mitosis & binary fission)
  • Sexual reproduction (meiosis & fertilization)

  
• Binary fission

  1. Prokaryotes such as bacteria divide into 2 identical cells

  2. Single chromosome makes a copy of itself

  3. Cell wall forms between the chromosomes dividing the cell

  
• Cell cycle


  A series of events that occur in a cell, leading to its division and the production of two daughter cells
• Cyclins

  Proteins that play a crucial role in regulating the progression of the cell cycle, particularly at key checkpoints. They work in conjunction with cyclin-dependent kinases (CDKs), forming complexes known as cyclin-CDK complexes.
• Stages of the cell cycle

  • G1 - primary growth phase
  • S - synthesis; DNA replicated
  • G2 - secondary growth phase
  • M - mitosis
  • C - cytokinesis

  
• G1 stage


  • 1st growth stage after cell division
  • Cells mature by making more cytoplasm & organelles
  • Cell carries on its normal metabolic activities
• G1 checkpoint


  The main decision point for a cell - where it checks cell size, nutrients, growth factors and DNA damage before deciding whether or not to divide
• S stage

  • Synthesis stage
  • DNA is copied or replicated
• G2 stage


  • 2nd Growth Stage
  • Cells continue to grow
  • Checks for DNA replication errors
  • Duplicates a microtubule-organizing structure called the centrosome

  
• G2 checkpoint


  Where the cell checks for DNA damage and DNA replication completeness
• Mitosis


  The process by which a cell replicates its chromosomes and then segregates them, into two genetically identical nuclei containing the same full set of DNA

  
• Mitosis

  1. Prophase - Chromosomes condense and become visible, spindle fibers start to form

  2. Metaphase - Chromosomes line up at the equator

  3. Anaphase - Sister chromatids are pulled apart to opposite poles

  4. Telophase - Daughter chromosomes reach opposite ends, nuclear envelope reforms

  5. Cytokinesis - Division of the cytoplasm into two daughter cells

  
• M checkpoint


  Also known as the spindle checkpoint - where the cell examines whether all the sister chromatids are correctly attached to the spindle microtubules

  
• Daughter cells of mitosis

  • Have the same number of chromosomes as each other and as the parent cell
  • Identical to each other, but smaller than parent cell
  • Must grow in size to become mature cells (G1 of Interphase)
• Eukaryotic cell division is used for growth and repair, producing two new cells identical to the original cell, with cells being diploid (2n)

  
• If mitosis is not controlled

  Unlimited cell division occurs causing cancerous tumors
• Oncogenes


  Special proteins that increase the chance that a normal cell develops into a tumor cell