L7

• What is the outcome of mitosis?


  Production of cells that are genetically identical to the parent
• What is the primary purpose of mitosis?

  It serves as the basis for producing new cells
• What is the outcome of meiosis?

  Production of cells with half the genetic content of the parent
• What is the primary purpose of meiosis?

  It serves as the basis for producing new sexually reproducing organisms
• What are the phases of the eukaryotic cell cycle?

  • G1 phase
  • S phase
  • G2 phase
• What occurs during the S phase of the cell cycle?

  DNA synthesis takes place
• What does interphase include?

  • Mitosis
  • Cytokinesis
• What happens during mitosis?

  The duplicated chromosomes are separated into 2 nuclei
• What is cytokinesis?


  The entire cell divides into 2 daughter cells
• What initiates the entry of a cell into M phase?

  A protein called "MPF"
• What are the components of MPF?

  1. A subunit with kinase activity
  2. A regulatory subunit called "cyclin"
• What happens to MPF levels as a cell enters M phase?


  MPF levels rise, activating the kinase
• What are cyclin-dependent kinases (Cdks)?

  They are the drivers that advance the cell cycle through its various stages
• When does the first transition point "START" occur in the cell cycle?

  In late G1 phase
• What happens when a cyclin reaches a sufficient concentration in the cell?

  It binds to the catalytic subunit of Cdk, changing the enzyme's active site
• What is the role of CAK in CDK phosphorylation?

  CAK phosphorylates Thr161, which is necessary but not sufficient for activation
• What does Wee1 do in CDK regulation?

  Wee1 phosphorylates Tyr15, keeping the Cdk in an inactive state
• What is the function of Cdc25 in CDK regulation?

  Cdc25 dephosphorylates Tyr15, activating the cyclin-Cdk complex
• What is the role of SCF complex in the cell cycle?

  It mediates the destruction of G1/S cyclins
• What does the degradation of Sic1 allow?

  It allows the cells to initiate DNA replication
• What is the function of the APC complex?

  It degrades mitotic cyclins, allowing a cell to exit mitosis
• What are the cell cycle checkpoints?

  1. Check for damaged chromosomal DNA
  2. Ensure critical processes like DNA replication and chromosome alignment are completed
• What happens if DNA is damaged beyond repair?

  The cell may undergo death or enter a state of permanent cell cycle arrest (senescence)
• What is Ataxia Telangiectasia (AT)?

  • An inherited recessive disorder
  • Increased risk for certain types of cancer
  • Extremely sensitive to ionizing radiation
• What is the role of the MRN protein complex in DNA damage response?

  It recruits proteins to sites of DNA breaks caused by ionizing radiation
• What does ATR kinase do when a cell is subjected to UV irradiation?

  ATR kinase is activated to prevent the cell from entering S phase
• How are cyclin-dependent kinases regulated?

  • They are constitutively expressed but inactive when not bound to cyclin
  • Tumor suppressors like P53 induce CDK inhibition
• What happens to telomerase in late S phase?

  Telomerase is activated on short telomeres that need to be elongated
• What is the significance of TP53 mutation in stem cells?

  It is likely to affect cell cycle regulation
• What is the relationship between cyclin D mutation and non-Hodgkin lymphoma?

  Cyclin D mutation is likely related to G1 phase regulation
• What is the effect of a telomerase inhibitor on the cell cycle?

  It is likely to affect the M phase of the cell cycle
• What is mitosis?


  A process of nuclear division where replicated DNA is segregated into 2 nuclei
• What is cytokinesis?


  A process where a dividing cell splits into two, partitioning the cytoplasm
• What are the stages of mitosis?

  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase
• What occurs during prophase?

  The chromosomes are in the form of extended filaments, and the nucleoli disappear
• What happens during metaphase?

  Chromosomes are aligned along the metaphase plate, attached to spindle poles
• What is karyotyping?


  • A process of ordering all chromosomes of an organism
  • Detection of numerical and structural chromosome anomalies
  • Usually analyzed during metaphase stage
• What occurs during anaphase?

  Centromeres split and chromatids separate, moving to opposite spindle poles
• What is the spindle assembly checkpoint (SAC)?

  It ensures chromosomes are properly aligned at the metaphase plate
• What happens during telophase?


  Chromosomes cluster at opposite spindle poles, and the nuclear envelope assembles around them