Powerpoint Import

• What are the main learning outcomes of the study material on the cell cycle?

  Describe the stages of the cell cycle, explain DNA replication, explain cytokinesis, describe signals inducing somatic cell division, and look at cell cycle disruption and cancer.
• How many pairs of chromosomes do humans normally have?

  23 pairs, totaling 46 chromosomes.
• What distinguishes autosomes from sex chromosomes in humans?

  Autosomes look the same in both males and females, while sex chromosomes differ between them.
• What are somatic cells?

  All cells of the body except sperm and egg cells.
• What is the difference between prokaryotic and eukaryotic cells?

  Prokaryotic cells have no nucleus or membrane-bound organelles, while eukaryotic cells contain them.
• What is mitosis?

  Division that results in two identical daughter cells.
• What is meiosis?

  Division that results in four sex cells (egg and sperm).
• What is cytokinesis?

  Cytoplasmic division that occurs after mitosis.
• What is apoptosis?

  Programmed and targeted cell death through internal signaling.
• What is necrosis?

  The death of most or all cells in an organ or tissue due to disease, injury, or failure of blood supply.
• Why is the cell cycle important?

  It is essential for replacing dead or injured cells and for tissue growth.
• How many cells does a human being go from at conception to adulthood?

  Around 75 trillion cells.
• What must be controlled during cell division?

  The sequence of events must be controlled to ensure proper division.
• What happens to cells that do not pass the G1 checkpoint?

  They do not proceed to the S phase and may enter G0.
• How long does the G1 phase last?

  About 8-10 hours of a 24-hour cycle.
• What occurs during the S phase of the cell cycle?

  DNA replication occurs, which is precise and accurate to prevent genetic abnormalities.
• How many pairs of chromosomes do human cells normally contain?

  23 pairs, for a total of 46 chromosomes
• What is the difference between somatic cells and sex cells (sperm and egg cells)?

  Somatic cells are all the cells of the body except sperm and egg cells
• What is the difference between mitosis and meiosis?

  Mitosis is cell division that results in two identical daughter cells, while meiosis is division that results in four sex cells (egg and sperm)
• What is the difference between apoptosis and necrosis?

  Apoptosis is programmed and targeted cell death due to internal signaling, while necrosis is the death of most or all cells in an organ or tissue due to external factors like disease, injury, or lack of blood supply
• Why is there a need for a balance between cell division and cell death?

  Because cells have a finite number of divisions, and uncontrolled cell division can lead to cancer, while too much cell death can lead to tissue atrophy
• What are the three main stages of the cell cycle?

  Interphase, mitotic (M) phase, and cytokinesis
• What are the three main phases of interphase?

  G1 phase, S phase, and G2 phase
• What is the main purpose of the G1 phase?

  Cells do not pass G1 without growth factors, it is a strictly controlled checkpoint with high metabolism, protein synthesis, and organelle duplication
• What is the main purpose of the S phase?

  DNA replication occurs, where the original DNA strands act as templates for the synthesis of new complementary strands
• What is the main purpose of the G2 phase?

  Synthesis of enzymes and proteins essential for cell division occurs, and replication of centrioles is completed
• What are the two main stages of the mitotic phase?

  Karyokinesis (nuclear division) and cytokinesis (cytoplasmic division)
• What are the four phases of mitosis?

  Prophase, metaphase, anaphase, and telophase
• What is the main feature of prophase in mitosis?

  Chromatin coils and condenses into bar-like chromosomes, with each chromosome now made of two chromatids
• What is the main feature of metaphase in mitosis?

  Chromosomes arrange themselves along the middle of the cell with the centromeres aligned at the equator of the spindle (metaphase plate)
• What is the main feature of anaphase in mitosis?

  The kinetochore of each chromatid splits, and the separated chromatids (now called daughter chromosomes) move towards opposite poles
• What is the main feature of telophase in mitosis?

  Chromosomes start uncoiling and transform into chromatin, the nuclear envelope reforms, and the mitotic spindle disappears
• What is the role of the kinetochore during cell division?

  The kinetochore is the protein structure on chromatids where the spindle fibres attach during cell division to pull sister chromatids apart
• How does the contractile ring form during cytokinesis?

  The actin cytoskeleton contracts, creating a cleavage furrow between the two cells, which continues until distinct membranes are formed
• What are the three main cell cycle checkpoints?

  G1 checkpoint, G2 checkpoint, and the mitotic spindle checkpoint
• What is the purpose of the cell cycle checkpoints?

  They verify whether the processes at each phase of the cell cycle have been accurately completed before progression into the next phase, and can stall the cell cycle for repairs or trigger apoptosis if damage is detected
• What is the restriction point in the cell cycle?

  It is a late G1 phase checkpoint where cells that should cease division exit the cell cycle and enter G0, and cells that continually divide overcome this barrier with cyclin D expression
• How do cyclins regulate the cell cycle?

  Cyclins bind to and activate cyclin-dependent kinases (Cdks), which regulate the initiation and progression of the cell cycle. The levels of cyclins rise and fall throughout the cycle to switch it on and off
• How are oncogenes and tumor suppressors related to the cell cycle?

  Oncogenes promote uncontrolled cell division, while tumor suppressors normally inhibit cell cycle progression. Disruption of the balance between these two leads to cancer, which is deregulated cell growth
• How does the mitotic spindle checkpoint work?

  The mitotic spindle checkpoint occurs at metaphase, ensuring all chromosomes are properly attached to the spindle fibers and under bipolar tension before allowing the cell to proceed to anaphase