BackBIOL 141 Chapter 12 Study Guide – Cell Cycle, Mitosis, and Cancer
Study Guide - Smart Notes
Tailored notes based on your materials, expanded with key definitions, examples, and context.
Q1. What is a chromosome? What is a chromatid? How many DNA double helices are present in an unreplicated chromosome or a replicated chromosome? How do sister chromatids differ from homologous chromosomes?
Background
Topic: Chromosome Structure and Terminology
This question tests your understanding of chromosome structure, the difference between chromatids and chromosomes, and the distinction between sister chromatids and homologous chromosomes.
Key Terms and Concepts:
Chromosome: A DNA molecule with associated proteins (histones) that carries genetic information.
Chromatid: One of two identical halves of a replicated chromosome.
Sister chromatids: The two identical DNA molecules formed by DNA replication, joined at the centromere.
Homologous chromosomes: Chromosomes of the same type (one from each parent) that carry the same genes but may have different alleles.
DNA double helix: The structure of DNA, consisting of two complementary strands.
Step-by-Step Guidance
Define what a chromosome is in the context of eukaryotic cells, focusing on its structure and function.
Explain what a chromatid is and how it relates to the chromosome, especially after DNA replication.
Consider the number of DNA double helices present in an unreplicated chromosome (before S phase) and in a replicated chromosome (after S phase, before cell division).
Clarify the difference between sister chromatids (identical copies from the same chromosome) and homologous chromosomes (similar but not identical, one from each parent).
Try answering these definitions and distinctions before checking the full explanation!
Q2. Draw a diagram showing the phases of the cell cycle. Describe the key events that occur during each stage.
Background
Topic: Cell Cycle Phases
This question tests your ability to identify and describe the main phases of the cell cycle and the events that occur in each phase.
Key Terms and Concepts:
G1 phase: Cell growth and normal functions.
S phase: DNA synthesis (replication).
G2 phase: Preparation for mitosis.
M phase (Mitosis): Division of the nucleus and cytoplasm.
Cytokinesis: Division of the cytoplasm.
Step-by-Step Guidance
List the main phases of the cell cycle in order: G1, S, G2, M.
For each phase, briefly describe the key events (e.g., what happens during G1, S, G2, and M phases).
Include cytokinesis as the final step, and note how it overlaps with the end of mitosis.
Sketch or visualize a circular diagram with each phase labeled and annotated with its main events.
Try drawing and labeling the cell cycle diagram before reviewing the full answer!
Q3. When during the cell cycle are chromosomes duplicated? If a diploid cell has 8 chromosomes during G1, how many DNA double helices will be present in G1? in G2? in metaphase? in each daughter cell after cell division is complete?
Background
Topic: DNA Replication and Chromosome Number
This question tests your understanding of when DNA replication occurs and how chromosome and DNA content changes throughout the cell cycle.
Key Terms and Concepts:
Diploid (2n): Two sets of chromosomes.
G1 phase: Before DNA replication.
G2 phase: After DNA replication, before mitosis.
Metaphase: Chromosomes aligned at the metaphase plate, each consisting of two sister chromatids.
Daughter cells: Cells produced after mitosis and cytokinesis.
Step-by-Step Guidance
Recall that DNA replication occurs during the S phase of the cell cycle.
In G1, count the number of DNA double helices (one per chromosome in a diploid cell).
After S phase (in G2 and metaphase), each chromosome consists of two sister chromatids, so count the total number of DNA double helices.
After cell division, determine how many DNA double helices are present in each daughter cell.
Try calculating the numbers for each phase before checking the answer!
Q4. Draw a diagram showing the steps of mitosis. Describe how sister chromatids are physically separated during the cell cycle, allowing each daughter cell to inherit a complement of chromosomes identical to the parent cell. What cell structures are required for this process?
Background
Topic: Mitosis and Chromosome Segregation
This question tests your understanding of the stages of mitosis, the mechanism of chromatid separation, and the cellular structures involved.
Key Terms and Concepts:
Mitosis stages: Prophase, Metaphase, Anaphase, Telophase.
Mitotic spindle: Structure made of microtubules that separates chromatids.
Centrosome: Organelle that organizes spindle fibers.
Kinetochore: Protein complex on chromatids where spindle fibers attach.
Step-by-Step Guidance
List and briefly describe each stage of mitosis (prophase, metaphase, anaphase, telophase).
Explain how the mitotic spindle attaches to kinetochores on sister chromatids.
Describe the process by which spindle fibers pull sister chromatids apart during anaphase.
Identify the key structures required for this process (spindle fibers, centrosomes, kinetochores).
Try sketching the steps and identifying the structures before reviewing the answer!
Q5. What happens during cytokinesis? Explain the role of the cytoskeleton in this process.
Background
Topic: Cytokinesis and Cytoskeletal Function
This question tests your understanding of how the cell physically divides after mitosis and the role of cytoskeletal elements in this process.
Key Terms and Concepts:
Cytokinesis: Division of the cytoplasm to form two daughter cells.
Actin filaments: Cytoskeletal proteins involved in forming the contractile ring in animal cells.
Myosin: Motor protein that interacts with actin to contract the ring.
Cell plate: Structure formed in plant cells during cytokinesis.
Step-by-Step Guidance
Describe the main event of cytokinesis: the division of the cytoplasm.
Explain how the contractile ring (in animal cells) or cell plate (in plant cells) forms.
Discuss the role of actin and myosin in animal cell cytokinesis.
Briefly mention how plant cells use vesicles to build a new cell wall (cell plate formation).
Try outlining the steps for both animal and plant cells before checking the answer!
Q6. What is MPF, and what are its components? How do the concentration of these components vary across the cell cycle? How does MPF act as a trigger for initiating M-Phase? What are the regulatory steps required for MPF activation? What causes the MPF concentration to decline sharply during M-Phase?
Background
Topic: Cell Cycle Regulation – MPF
This question tests your understanding of the molecular control of the cell cycle, specifically the role of MPF (Maturation Promoting Factor).
Key Terms and Concepts:
MPF (Maturation Promoting Factor): A complex that triggers the cell's entry into mitosis.
Cyclin: Regulatory protein whose concentration fluctuates during the cell cycle.
Cdk (Cyclin-dependent kinase): Enzyme that, when bound to cyclin, becomes active.
Phosphorylation: Addition of a phosphate group, regulating protein activity.
Step-by-Step Guidance
Identify the two main components of MPF and describe their roles.
Explain how the concentration of cyclin changes during the cell cycle, and how this affects MPF activity.
Describe how MPF triggers the onset of M-phase (mitosis).
Outline the regulatory steps required for MPF activation, including phosphorylation and dephosphorylation events.
Discuss what leads to the rapid decline in MPF activity during M-phase.
Try explaining each regulatory step before checking the answer!
Q7. What category of proteins transfer a phosphate group to substrates? Give an example of one such protein that plays a role in cell cycle regulation.
Background
Topic: Protein Kinases and Cell Cycle Control
This question tests your knowledge of enzymes that modify other proteins by phosphorylation and their role in cell cycle regulation.
Key Terms and Concepts:
Kinase: An enzyme that transfers phosphate groups from ATP to target proteins.
Cyclin-dependent kinase (Cdk): A kinase involved in cell cycle regulation.
Phosphorylation: The process of adding a phosphate group to a molecule.
Step-by-Step Guidance
Name the category of enzymes that transfer phosphate groups to substrates.
Provide an example of a kinase involved in cell cycle regulation.
Briefly describe how this kinase functions in the context of the cell cycle.
Try recalling the enzyme category and an example before checking the answer!
Q8. What are cell cycle checkpoints? Where in the cell cycle are the checkpoints found? How do they differ? How are Rb, p53, and MPF involved in cell cycle checkpoints? What events could lead to cell cycle arrest?
Background
Topic: Cell Cycle Checkpoints and Regulation
This question tests your understanding of the mechanisms that monitor and regulate progression through the cell cycle.
Key Terms and Concepts:
Checkpoint: A control point where the cell cycle can be halted until certain conditions are met.
G1 checkpoint: Checks for DNA damage, cell size, and growth factors.
G2 checkpoint: Checks for DNA replication completion and damage.
M checkpoint: Ensures chromosomes are properly attached to the spindle.
Rb (Retinoblastoma protein): Tumor suppressor involved in G1 checkpoint.
p53: Tumor suppressor that can induce cell cycle arrest or apoptosis.
MPF: Regulates entry into mitosis.
Step-by-Step Guidance
List the main cell cycle checkpoints and where they occur (G1, G2, M).
Describe the main function of each checkpoint and how they differ.
Explain the roles of Rb, p53, and MPF in checkpoint control.
Identify events that could trigger cell cycle arrest at these checkpoints.
Try mapping out the checkpoints and their regulators before checking the answer!
Q9. Explain the cellular basis of cancer. What defects are commonly found in cancer cells? Do all cancer cells have mutations in the same genes? Explain.
Background
Topic: Cancer Biology and Cell Cycle Regulation
This question tests your understanding of how defects in cell cycle regulation can lead to cancer, and the genetic diversity of cancer cells.
Key Terms and Concepts:
Uncontrolled cell division: Hallmark of cancer.
Oncogenes: Mutated genes that promote cell division.
Tumor suppressor genes: Genes that normally inhibit cell division or promote apoptosis.
Genetic heterogeneity: Different cancers have different mutations.
Step-by-Step Guidance
Describe how normal cell cycle regulation prevents uncontrolled division.
Explain what happens when these regulatory mechanisms fail (e.g., mutations in oncogenes or tumor suppressors).
List common defects found in cancer cells (e.g., loss of checkpoint control, evasion of apoptosis).
Discuss whether all cancer cells share the same mutations or if there is genetic diversity among cancers.
Try outlining the main defects and their consequences before checking the answer!
Q10. What are growth factors, and what role do they play in the control (or loss of control) of the cell cycle? What is the relationship of cancer to the G1 checkpoint?
Background
Topic: Growth Factors and Cell Cycle Control
This question tests your understanding of how external signals regulate the cell cycle and how their misregulation can contribute to cancer.
Key Terms and Concepts:
Growth factors: Extracellular signals that stimulate cell division.
Signal transduction: Process by which cells respond to growth factors.
G1 checkpoint: Point where the cell commits to division, influenced by growth factors.
Cancer: Often involves loss of growth factor dependence or checkpoint control.
Step-by-Step Guidance
Define growth factors and their general role in cell signaling.
Explain how growth factors influence progression through the G1 checkpoint.
Describe what happens when cells lose the requirement for growth factors (as in many cancers).
Discuss the connection between loss of G1 checkpoint control and cancer development.
Try explaining the role of growth factors and the G1 checkpoint before checking the answer!
