3.2.2 All cells arise from other cells

• Cytokinesis is the process that follows mitosis, during which the cytoplasm divides and two daughter cells are formed.
• Interphase is the phase that occurs before mitosis, during which the cell grows, replicates its DNA, and prepares for cell division.
• Telophase is the final stage of mitosis, during which the nuclear envelope reforms around the separated sister chromatids and the chromosomes decondense into chromatin.
• Eukaryotic cells that do not retain the ability to divide go through a cell cycle before mitosis.
• The first growth phase (G1) involves cell growth and replication of organelles.
• The G1 checkpoint verifies if DNA has been damaged, growth factors, cell size, and nutrients.
• The synthesis phase (S) involves DNA replication.
• The second growth phase (G2) involves further cell growth and development of organelles and proteins.
• The G0 stage is where the cell moves out of the cell cycle, which can be temporary or permanent due to differentiation or DNA damage.
• Mitosis involves several stages: prophase, metaphase, anaphase, and telophase.
• During prophase, chromosomes condense and centrioles move to opposite poles of the cell, forming a spindle.
• During metaphase, chromosomes line up at the equator of the spindle and spindle fibers attach to centromeres.
• During anaphase, centromeres divide, separating sister chromatids, and spindles shorten, pulling chromatids to opposite poles of the cell.
• Cancer is caused by uncontrollable cell division which is a result of a mutation in the gene that controls mitosis
• Cancer treatments are directed at controlling rate of cell division
• chromosomes are?

  long, condensed DNA molecule
• chromatin is?

  complex of DNA wrapped around histones
• chromatids are?

  one strand of a replicated chromosome
• Centromere is?

  point at which chromatids are joined
• homologous chromosomes are?

  pair of chromosomes - one originating from each parent, containing the same genes but different alleles
• Chemotherapy prevents synthesis of enzymes in G1 needed for DNA replication in S phase so cell cannot enter S phase leading cell to kill itself
• what phase of the cell cycle does chemotherapy target?

  G1
• Radiation and some drugs damage DNA. At several points in the cell cycle (including just before and during S phase) the DNA in the cell is checked for damage.

  If severe damage is detected, the cell will kill itself — preventing further tumour growth.
• what phase of the cell cycle does radiation and some drugs target?

  S
• binary fission in prokaryotic cells involves:

  • replication of circular DNA and of plasmids
  • division of cytoplasm to produce 2 daughter cells, each with a single copy of circular DNA and a variable number of copies of plasmids
• Being non-lining, viruses do not undergo cell division. Following injection of their nucleic acid, the infected host cell replicates their virus particles.
• Why do we leave the root tips in acid for around 5 minutes?

  to soften and loosen the root tissue.
• 1. Warm hydrochloric acid in a water bath at 60°C.
  2. Cut 1-2cm of root tip using scalpel from a growing root
  3. Wash the root tips in cold water; dry on filter paper.
  4. Leave the root tips in the acid for around 5 minutes
  5.  Remove the root tips from acid and then wash them again in cold water and dry on filter paper.
  6. Place the root tip on a clean slide.
  7. Add a few drops of stain to the root tips; leave for 2 minutes. 
  8. Use a mounted needle to break up the tissue; spread the cells of the root tip out onto the slide.
  9. use a mounted needle to lower the cover slip and press down

   
• The stages of cell cycle include interphase, mitosis and cytokenesis.