Lecture 42: Cell divison, the cell cycle and its controllers Flashcards
Flashcards for Lecture 42 – The Cell Cycle
- Q: What is the cell cycle?
A: The cell cycle is an ordered series of events that lead to cell growth
DNA replication
- Q: Why is the cell cycle important?
A: It ensures proper cell growth
development
- Q: What are the two major phases of the cell cycle?
A: Interphase (where the cell grows and prepares for division) and the Mitotic (M) phase (where the cell divides).
- Q: What are the three stages of Interphase?
A: G1 (growth and preparation)
S (DNA replication)
- Q: What occurs during G1 phase?
A: The cell grows
synthesizes proteins
- Q: What happens in the S phase?
A: DNA replication occurs
producing two identical copies of each chromosome.
- Q: What is the G2 phase
and why is it important?
A: The G2 phase is when the cell prepares for mitosis by synthesizing proteins and organelles and ensuring DNA replication is complete.
- Q: What are the key stages of mitosis?
A: Prophase
Metaphase
- Q: Describe Prophase.
A: Chromatin condenses into visible chromosomes
the nuclear envelope disintegrates
- Q: What happens in Metaphase?
A: Chromosomes align at the metaphase plate
and spindle fibers attach to the centromeres.
- Q: Explain Anaphase.
A: Sister chromatids separate and move to opposite poles
pulled by the spindle fibers.
- Q: What is Telophase?
A: Chromosomes decondense into chromatin
the nuclear envelope reforms
- Q: What is cytokinesis
and when does it occur?
A: Cytokinesis is the division of the cytoplasm
occurring after telophase
- Q: What proteins regulate the cell cycle?
A: Cyclins and cyclin-dependent kinases (CDKs)
which control progression through checkpoints.
- Q: What is the purpose of the G1 checkpoint?
A: To ensure the cell has sufficient nutrients
undamaged DNA
- Q: What happens if a cell does not pass the G1 checkpoint?
A: The cell enters G0
a resting phase where it does not divide but may re-enter the cycle later.
- Q: What does the G2 checkpoint do?
A: It verifies that DNA replication was successful and that the cell is ready for mitosis.
- Q: What is the M checkpoint?
A: It ensures all chromosomes are correctly attached to spindle fibers before anaphase begins.
- Q: How does the tumor suppressor protein p53 regulate the cell cycle?
A: p53 halts the cell cycle if DNA damage is detected
allowing for repair or triggering apoptosis if damage is irreparable.
- Q: What happens when cell cycle regulation fails?
A: Uncontrolled cell division can occur
leading to tumor formation and cancer.
- Q: Why is the cell cycle a target for cancer treatment?
A: Cancer cells divide uncontrollably
so targeting specific cycle phases can inhibit tumor growth.
- Q: What are some drugs that target the cell cycle?
A: Chemotherapy drugs like Taxol (stabilizes microtubules) and CDK inhibitors (block cyclin-CDK complexes).
- Q: How does Taxol work?
A: It prevents microtubule disassembly
blocking mitosis and causing cell death.
- Q: What are CDK inhibitors
and how do they work?
A: They block CDK activity
halting the cell cycle and preventing cancer cell proliferation.
- Q: How do researchers analyze the cell cycle in a lab?
A: Techniques like flow cytometry and fluorescent microscopy help assess DNA content and cell cycle phases.
- Q: How is flow cytometry used to study the cell cycle?
A: It measures DNA content in cells to determine their position in the cell cycle.
- Q: What is apoptosis
and how is it linked to the cell cycle?
A: Apoptosis is programmed cell death
which removes damaged cells if checkpoints detect irreparable DNA damage.
- Q: How do growth factors influence the cell cycle?
A: Growth factors signal cells to divide by promoting cyclin and CDK activation.
- Q: How does contact inhibition affect the cell cycle?
A: Cells stop dividing when they come into contact with neighboring cells
preventing overgrowth.
- Q: What is the role of telomeres in the cell cycle?
A: Telomeres protect chromosome ends; their shortening limits cell division and contributes to aging.
- Q: What enzyme extends telomeres
and why is it significant?
A: Telomerase
which is active in stem cells and cancer cells
- Q: How do oncogenes contribute to uncontrolled cell division?
A: Oncogenes are mutated genes that promote excessive cell growth and bypass checkpoints.
- Q: What are tumor suppressor genes
and why are they important?
A: They prevent uncontrolled division by repairing DNA or triggering apoptosis when necessary.
- Q: How do mutations in tumor suppressor genes lead to cancer?
A: Loss-of-function mutations disable the cell’s ability to halt division or repair DNA damage.
- Q: What is the significance of the Rb protein in cell cycle control?
A: It prevents excessive cell growth by inhibiting transcription factors required for S phase entry.
- Q: What is the role of E2F in the cell cycle?
A: E2F is a transcription factor that promotes DNA replication
activated when Rb is inactivated.
- Q: What is the function of mitogens in cell cycle regulation?
A: Mitogens stimulate cell division by promoting cyclin expression.
- Q: How does the spindle assembly checkpoint prevent chromosome missegregation?
A: It delays anaphase until all chromosomes are properly attached to spindle fibers.
- Q: Why do cancer cells often have chromosomal instability?
A: They bypass cell cycle checkpoints
leading to unequal chromosome distribution.
- Q: What is the difference between benign and malignant tumors?
A: Benign tumors remain localized
while malignant tumors invade tissues and metastasize.
