Topic 3 - The Voice of the Genome

• Chromosomes are only visible during cell division
• Rough ER has ribosomes attached and are involved in further processing enzymes and proteins
• Smooth ER has no ribosomes and is involved in the synthesis of lipids, cholesterol and steroid hormones
• The golgi complex is a system of sacs used to package proteins and lipids in vesicles
• Lysosomes are small vesicles in the cytoplasm containing digestive enzymes to digest substances or even digest parts of/ the entire cell
• Mitochondria have double membranes
• The cytoskeleton is made up of 3 elements:

  • Microfilaments
  • Intermediate filaments
  • Microtubules
• In prokaryotic cells do not have their DNA bound around histones
• Prokaryotic cells do have ribosomes but they're smaller
• Prokaryotic cell walls are made of peptidoglycan
• Some prokaryotic cells have slime capsules for hydration and protection
• Meselson and Stahl proposed that DNA is a semi-conservative molecule, they did this by:

  • Growing E-coli in an N15 environment
  • Initially, the DNA was very heavy going through the centrifuge
  • They then grew the bacteria in N14
  • After 1 cell division the DNA was half as heavy
  • Several divisions later, there were 2 bands, a light one and one half as heavy
• The acrosome in sperm cells contains digestive enzymes
• Acrosome reaction involves entering the egg cell
• Cortical reaction stops other sperm cells from getting in the egg cell
• 1. Sperm cells reach the egg
  2. Chemicals released from the follicle cells trigger acrosome reactions
  3. The acrosome swells and digestive enzymes are released
  4. The enzyme digests the follicle cells
  5. The sperm cell digests the zona pellucida
  6. The sperm fuses with the egg membrane and its nucleus enter
  7. Enzymes released by ovarian lysosomes harden the zona pellucida
  8. The nucleus of the sperm and egg fuse
• Teratozoospermia is a condition where sperm have abnormal morphology that affects fertility in males
• A homologous pair of chromosomes are those that match in length and contain the same genes at the same loci
• The allele for sex-linked disorders is located on the X chromosome meaning males are much more likely to have it as they only have 1 copy
• A tissue is a group of similar specialised cells that work together to perform a specific function
• Interphase is the first stage of mitosis, the DNA is replicating and chromosomes are not yet visible
• During prophase centrioles move to opposite poles of the cell. Spindle fibres begin to develop and chromosones are no visible
• During metaphase, spindle fibers attach to the chromatids and line up in the middle of the cell
• During anaphase, spindle fibers contract and chromatids are pulled apart
• During telophase, the nuclear membrane begins to reform, spindle fibers disappear and chromosomes become indistinct
• Interphase is the first stage of mitosis, DNA replicates and chromosomes are not visible
• Prophase is the second stage of mitosis, centrioles move to opposite poles and spindle fibres begin to develop, the nuclear membrane starts to break down and chromosomes become visible
• Metaphase is the third stage of mitosis, spindle fibres attach to chromatids and the chromatids line up across the middle of the cell
• Anaphase is the fourth stage of mitosis, spindle fibres contract and pull individual chromatids
• Telophase is the fifth stage of mitosis, spindle fibres disappear and the nuclear membrane begins to reform
• The cell cycle has 3 phases:

  • G1
  • S
  • G2
• G1 is the first growth phase: the cell grows new organelles and increases in size
• S (synthesis) is the second stage of the cell cycle: DNA replication begins to take place
• G2 is the second growth phase: the cell grows and prepares for mitosis
• The ability of stem cells to differentiate is called potentcy
• A fertilised human egg cell develops into a blastocyst which is a bundle of stem cells
• Fully specialised cells can not divide by mitosis
• Adult stem cells are found in bone marrow, the brain and blood
• A totipotent stem cell can differentiate into anything including umbilical and placental cells
• A pluripotent stem cell can differentiate into anything except for umbilical and placental cells