2.2 cell replication

• within multicellular organisms, not all cells retain the ability to divide
• cell division in eukaryotic cells is mitosis
• mitosis process

  interphase: G1, S, G2

  mitosis: prophase, metaphase, anaphase, telophase

  cytokinesis
• mitosis features

  • one division
  • 2 genetically identical daughter cells
  • for growth, repair, and asexual reproduction
• G1 - cellular contents, minus the chromosomes, are duplicated
• S - each of the 46 chromosomes are duplicated
• G2 - cell double checks the duplicated chromosomes for any errors, repairing as needed
• prophase - chromosomes become visible, nuclear envelope disintegrates, nucleolus disappears
• metaphase - spindle fibres attach to centromeres of chromosomes and arrange the chromosomes around the equator of the cell
• anaphase - centromeres divide into two and spindle fibres pull the individual chromatids, pulling the chromosome apart towards the opposite poles of the cell
• telophase - chromosomes reach the poles and become indistinct, nuclear envelope reforms, nucleolus reforms, spindle fibres disintegrate
• cytokinesis - cytoplasm and cell membrane divide, two genetically identical cells are formed
• • mitosis is a controlled process
  • uncontrolled cell division can lead to the formation of tumours and cancers
• cancer treatments are directed at controlling the rate of cell division
• cell division in prokaryotic cells is binary fission
• binary fission process:

  1. circular DNA molecule replicated and both copies attach to the cell membrane
  2. plasmids replicate
  3. cell membrane begins to grow between two DNA molecules and begins to pinch inwards, dividing the cytoplasm into two
  4. a new cell wall forms between two identical molecules of DNA, dividing the original cell into two identical daughter cells, each with a single copy of the circular DNA and a variable number of copies of the plasmids
• viruses do not undergo cell division as they are non-living
• replication of viruses:

  1. attach to host cell with attachment proteins on their surface
  2. inject nucleic acids into the host cell
  3. genetic information in nucleic acids provides instructions for host cell's metabolic processes to start producing viral components (nucleic acids, enzymes) which are then assembled into new viruses
• making a microscope slide

  1. place one drop of water onto a slide
  2. use forceps to remove piece of [specimen] tissue and place it flat onto the water
  3. add two drops of iodine solution to stain the [specimen] tissue
  4. gently lower a coverslip over specimen. use a mounted needle to reduce the likelihood of air bubbles
  5. use a piece of filter paper to absorb excess stain

  examine specimen using high power