eukaryotic cytoskeleton and mitosis

• What are the three cytoskeletal elements commonly found in eukaryotic cells?

  Actin filaments, microtubules, intermediate filaments
• Why are intermediate filaments called "intermediate"?

  They are between thick and thin filaments
• What are actin filaments built up of?

  Two main chains of actin globular monomers
• What determines the polarity of actin filaments?

  Subunits are organized with the same polarity
• Where does assembly of actin filaments occur fastest?

  At the positive end of the filament
• What role does ATP play in actin assembly?

  ATP favors assembly of actin filaments
• What is the diameter of microtubules?

  Approximately 28 nm
• What are microtubules composed of?

  Globular alpha and beta tubulin
• What is the protomer for microtubule assembly?

  A heterodimer of alpha and beta tubulin
• What phenomenon do microtubules exhibit?

  Dynamic instability, growing and shrinking rapidly
• What is the role of microtubules during mitosis?

  They separate sister chromatids
• What proteins transport cargoes along microtubules?

  Kinesin and dynein
• Where is gamma tubulin found?

  At the centrosome
• What is the function of gamma tubulin in microtubule assembly?

  Acts as a site of nucleation
• What is the diameter of intermediate filaments?

  10 nm
• How do intermediate filaments form?

  From soluble tetramers to protofilaments
• How do intermediate filaments compare to actin and microtubules?

  Less dynamic than actin and microtubules
• What is the primary function of intermediate filaments?

  To provide structural strength to the cell
• What causes HGPS (Progeria)?

  Defects in lamin A
• How is HGPS inherited?

  Autosomal dominant form of inheritance
• What characterizes children with HGPS?

  Premature aging and unique appearance
• What percentage of LMNA mutations in progeria patients are classical p.G608G mutations?

  76%
• What is Epidermolysis Bullosa Simplex commonly known as?

  Butterfly skin
• What causes Epidermolysis Bullosa Simplex?

  Keratin defects
• What are the stages of mitosis?

  1. Interphase: Cell increases in size, DNA replicates, centrosome duplicates.
  2. Prophase: Chromosomes condense, spindle assembles.
  3. Prometaphase: Nuclear envelope breaks down, chromosomes attach to spindle.
  4. Metaphase: Chromosomes align at spindle equator.
  5. Anaphase: Sister chromatids separate and move to poles.
  6. Telophase: Daughter chromosomes arrive at poles, nuclear envelope reassembles.
  7. Cytokinesis: Daughter cells physically separate.
• What happens during interphase of the cell cycle?

  The cell increases in size and DNA replicates
• What occurs during prophase of mitosis?

  Chromosomes condense and spindle assembles
• What marks the start of prometaphase?

  Breakdown of the nuclear envelope
• What happens during metaphase of mitosis?

  Chromosomes align at the equator of the spindle
• What occurs during anaphase of mitosis?

  Sister chromatids separate and move to poles
• What happens during telophase of mitosis?

  Daughter chromosomes arrive at poles and nuclear envelope reassembles
• What begins the process of cytokinesis?

  Assembly of contractile rings
• What is the final outcome of cytokinesis?

  Daughter cells physically separate