CELL DIVISION

• Mitosis

  • Asexual reproduction
  • results in offspring that are genetically identical to lone parent
  • ordinary cell division
  • enables multicellular organisms to grow and develop to replace damaged or lost cells
  • 2 identical daughter cells
• Meiosis

  • sexual reproduction
  • union of sperm and egg cell
  • type of cell division that yields gametes with only half as many chromosomes as somatic cells
  • divides twice to form four daughter cells
• Cell Cycle


  An ordered sequence of events that extends from the time a cell is formed from a dividing parent cell until its own division into two cells.
• Interphase


  A time when a cell goes about its usual business, performing its normal functions within the organism
• G1 Phase (interphase)


  First gap/checkpoint
• S Phase (interphase)


  Synthesis of DNA also known as DNA replication
• G2 PHASE


  Second gap/checkpoint and completes preparations for cell division
• Cytokinesis


  Where the cytoplasm is divided into two.
• Prophase


  The start of mitosis where the chromosomes coil up and the nuclear envelope breaks down.
• Metaphase


  A mitotic spindle made of microtubule tracks moves the chromosomes to the middle of the cell.
• Anaphase


  The sister chromatids then separate and are moved to opposite poles to the cell.
• Telophase


  Two new nuclei form.
• Somatic each species contain a specific number of chromosomes; human cells have 46, made up of 23 pairs of homologous chromosomes.
• Mamallian Males - have X and Y sex chromosomes

  Females - have two X chromosomes
• Meiosis I


  Starts with pairing of homologous chromosomes.

  In crossing over, they exchange corresponding segments.

  Separation of the members of the homologous pairs and produces two daughter cells, each with one set of duplicated chromosomes.
• Meiosis II


  Essentially the same as mitosis. In each of the cells, the sister chromatids of each chromosome separate.