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What happens to a eukaryotic cell before it divides?
What happens to a eukaryotic cell before it divides?
Which phase follows the G₂ phase in the cell cycle?
Which phase follows the G₂ phase in the cell cycle?
Which statement is true regarding the G₀ phase?
Which statement is true regarding the G₀ phase?
What characterizes the transition from interphase to mitotic phase?
What characterizes the transition from interphase to mitotic phase?
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How often do blood cells typically divide in a eukaryotic organism?
How often do blood cells typically divide in a eukaryotic organism?
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What consequence does excessive cell division often lead to?
What consequence does excessive cell division often lead to?
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What is primarily accumulated during the G₁ phase?
What is primarily accumulated during the G₁ phase?
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What is a major function of the checkpoints in the cell cycle?
What is a major function of the checkpoints in the cell cycle?
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What is indicated by the presence of the Philadelphia chromosome?
What is indicated by the presence of the Philadelphia chromosome?
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Which characteristic is NOT a general trait of cancerous cells?
Which characteristic is NOT a general trait of cancerous cells?
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During which phase do errors leading to uncontrolled cell growth typically occur?
During which phase do errors leading to uncontrolled cell growth typically occur?
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Which of the following treatment approaches aims to create problems for cancerous cells?
Which of the following treatment approaches aims to create problems for cancerous cells?
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What does metastasis refer to in cancer biology?
What does metastasis refer to in cancer biology?
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What happens to p53 if it undergoes a mutation?
What happens to p53 if it undergoes a mutation?
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Which enzymes are primarily responsible for unwinding DNA during replication?
Which enzymes are primarily responsible for unwinding DNA during replication?
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During the S-phase, how many copies of each chromosome are created?
During the S-phase, how many copies of each chromosome are created?
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In which phase do chromosomes begin to form nucleosomes?
In which phase do chromosomes begin to form nucleosomes?
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What role do DNA topoisomerases play in DNA replication?
What role do DNA topoisomerases play in DNA replication?
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Which statement is true about cells in the G₀ phase?
Which statement is true about cells in the G₀ phase?
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What occurs to the sister chromatids during the S-phase?
What occurs to the sister chromatids during the S-phase?
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What is the characteristic composition of chromosomes during the G₁ phase?
What is the characteristic composition of chromosomes during the G₁ phase?
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Which enzyme is primarily responsible for unwinding the double strands of DNA during the S-phase?
Which enzyme is primarily responsible for unwinding the double strands of DNA during the S-phase?
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What event occurs during the G2-phase of the eukaryotic cell cycle?
What event occurs during the G2-phase of the eukaryotic cell cycle?
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During which phase of mitosis do kinetochores appear at the centromeres?
During which phase of mitosis do kinetochores appear at the centromeres?
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In which stage of the cell cycle is the amount of DNA in the cell double?
In which stage of the cell cycle is the amount of DNA in the cell double?
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What is the function of topoisomerase in DNA replication?
What is the function of topoisomerase in DNA replication?
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Which of the following correctly describes the role of spindle fibers during metaphase?
Which of the following correctly describes the role of spindle fibers during metaphase?
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What characterizes the cell during the G0 phase?
What characterizes the cell during the G0 phase?
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What occurs during cytokinesis in animal cells?
What occurs during cytokinesis in animal cells?
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What is the role of p53 in cellular function?
What is the role of p53 in cellular function?
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What occurs during anaphase in mitosis?
What occurs during anaphase in mitosis?
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Which process leads to the formation of a cleavage furrow in animal cells?
Which process leads to the formation of a cleavage furrow in animal cells?
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What is a potential consequence of errors during metaphase?
What is a potential consequence of errors during metaphase?
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What type of chromosomal alteration occurs if a portion of a chromosome is lost and attaches to a different chromosome?
What type of chromosomal alteration occurs if a portion of a chromosome is lost and attaches to a different chromosome?
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Which phase of mitosis involves chromosomes being lined up at the metaphase plate?
Which phase of mitosis involves chromosomes being lined up at the metaphase plate?
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What kind of cellular abnormality is characterized by having an extra or missing chromosome?
What kind of cellular abnormality is characterized by having an extra or missing chromosome?
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Which of the following statements about kinetochores is true?
Which of the following statements about kinetochores is true?
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Study Notes
Eukaryotic Cell Cycle
- Eukaryotic cells have a definite nucleus, enclosed by a nuclear envelope.
- Cells divide to replace dead or missing cells via a regulated sequence of events.
- Division is stimulated by growth factors and inhibited by growth suppressors.
- Cell division timing varies by cell type, from every 30 minutes for embryonic cells to every 3 months for blood cells.
- Abnormal cell division can lead to cancer (too frequent) or cell death (apoptosis, not enough).
Cell Division Processes
- The eukaryotic cell cycle consists of two main phases:
- Interphase: The cell is not dividing and preparing for mitosis.
- Mitotic Phase (M): The cell divides, with replicated genetic material distributed to two daughter cells.
- Interphase is further divided into three sub-phases:
- G₁: First gap phase, where the cell accumulates building blocks for DNA, proteins, and energy reserves.
- S: Synthesis phase, where DNA replicates, creating an exact copy of each chromosome, resulting in sister chromatids attached at the centromere.
- G₂: Second gap phase, where the cell replenishes energy, synthesizes proteins needed for chromosome manipulation, duplicates organelles, and prepares for the mitotic spindle.
- Mitosis is further divided into five sub-phases:
- Prophase: Chromosomes condense, spindle fibers form from centrosomes, and the nuclear envelope breaks down.
- Prometaphase: Chromosomes condense further, kinetochores appear at the centromeres, and spindle microtubules attach to them.
- Metaphase: Chromosomes line up at the metaphase plate, with each sister chromatid attached to a spindle fiber originating from opposite poles.
- Anaphase: Centromeres split, separating sister chromatids (now called chromosomes) and pulling them towards opposite poles. Spindle fibers elongate the cell.
- Telophase: Chromosomes arrive at opposite poles, decondense, and are enveloped by new nuclear membranes. The mitotic spindle breaks down, and spindle fibers continue pushing poles apart.
G₁-Phase
- The first gap phase of interphase, where the cell is not actively dividing, but is preparing.
- Biochemical events during G₁ involve:
- Semi-condensed chromosomes, forming nucleosomes and chromatin fibers.
- Regulation by positive (growth factors) and negative (growth suppressors) regulators of growth and division.
- p53 is a key regulator that inhibits the cycle in G₁. If mutated, it can lead to loss of control and potentially cancer.
S-Phase (DNA Replication)
- The synthesis phase of interphase, where DNA is replicated.
- DNA remains in the semi-condensed chromatin structure formed during G₁.
- Replication requires various enzymes:
- DNA topoisomerase relaxes supercoiled DNA by temporarily cutting the backbone of one or both DNA strands.
- Helicases unwind the DNA double strands to create replication forks.
- DNA polymerases synthesize sister chromatids for each chromosome using complementary base pairing (A-T and G-C).
- This results in the cell having twice the amount of DNA needed.
G₂-Phase
- The second gap phase of interphase, where the cell completes final preparations.
- It involves replenishing energy stores, synthesizing proteins needed for mitosis, duplicating organelles, and preparing resources for the mitotic spindle.
M-Phase & Cytokinesis
- Mitosis and cytokinesis involve:
- Mitosis: The process of dividing the nucleus and chromosomes into two identical daughter nuclei.
- Cytokinesis: The division of the cytoplasm, forming two daughter cells.
- Mitosis occurs in five phases, as described above.
- Cytokinesis differs for animal and plant cells:
- Animal cells: A cleavage furrow separates the daughter cells.
- Plant cells: A cell plate forms, eventually becoming a new cell wall between daughter cells.
Mitosis Gone Wrong
- Errors during mitosis can lead to:
- Aneuploidy: Cells with extra or missing chromosomes, which can result in syndromes, cancers (e.g. Down Syndrome, leukemia).
- Chromosome damage: Breaks, deletions, inversions, or translocations due to errors in separation.
Cancer
- Uncontrolled cell growth is a hallmark of cancer.
- Tumors are clusters of cancerous cells undergoing uncontrolled mitosis.
- If cancerous cells spread to other locations, it's called metastasis.
- Cancerous cells exhibit different traits like uncontrolled mitosis, faster growth, and abnormal structure.
Cancer Treatment
- Treatment approaches include:
- Fixing the problem: E.g., bone marrow transplants.
- Creating problems for cancerous cells: Interfering with mitosis via various medications and therapies.
Questions
- The eukaryotic cell cycle consists of Interphase, which prepares the cell for division, and the Mitotic Phase, where the cell divides.
- The G₁ checkpoint ensures the cell has the necessary building blocks for DNA replication, protein synthesis, and energy reserves.
- The M checkpoint ensures that chromosomes are correctly aligned at the metaphase plate before proceeding to anaphase.
- The eukaryotic cell cycle is crucial for growth, development, and repair of organisms.
- The text highlights the importance of understanding the cell cycle for developing effective cancer treatments.
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Description
Explore the intricate processes of the eukaryotic cell cycle, including the phases of interphase and mitosis. Understand the role of growth factors in cell division and how abnormal division can contribute to cancer. This quiz will test your knowledge on key concepts and terminology related to cell division.
