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Questions and Answers
What is the primary function of a cell during interphase?
What is the primary function of a cell during interphase?
Which of the following best describes the sequence of phases in the cell cycle?
Which of the following best describes the sequence of phases in the cell cycle?
During which phase of the cell cycle does DNA replication occur?
During which phase of the cell cycle does DNA replication occur?
What characterizes the G1 phase of the cell cycle?
What characterizes the G1 phase of the cell cycle?
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If a cell is not actively dividing, in which phase of the cell cycle would it most likely be found?
If a cell is not actively dividing, in which phase of the cell cycle would it most likely be found?
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Approximately how long does the S phase, where chromosome replication occurs, typically lasts?
Approximately how long does the S phase, where chromosome replication occurs, typically lasts?
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What is the consequence of un-replicated areas of DNA during the S phase?
What is the consequence of un-replicated areas of DNA during the S phase?
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Which of the following statements is true about observable changes during interphase?
Which of the following statements is true about observable changes during interphase?
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What is the primary function of meiosis I?
What is the primary function of meiosis I?
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During which stage of meiosis I does synapsis occur?
During which stage of meiosis I does synapsis occur?
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What is the consequence of non-disjunction during Anaphase II?
What is the consequence of non-disjunction during Anaphase II?
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Which event occurs during the pachytene stage of prophase I?
Which event occurs during the pachytene stage of prophase I?
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How many cells result from one round of meiosis?
How many cells result from one round of meiosis?
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Which cyclin is primarily responsible for promoting entry into the cell cycle?
Which cyclin is primarily responsible for promoting entry into the cell cycle?
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What is the name of the complex that forms during synapsis?
What is the name of the complex that forms during synapsis?
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What is the ploidy of the cells at the end of meiosis I?
What is the ploidy of the cells at the end of meiosis I?
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At which stage of the cell cycle are S-phase cyclins synthesized?
At which stage of the cell cycle are S-phase cyclins synthesized?
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What process primarily regulates cyclin levels during the cell cycle?
What process primarily regulates cyclin levels during the cell cycle?
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What is the status of the nuclear membrane during diakinesis?
What is the status of the nuclear membrane during diakinesis?
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Which cyclin is responsible for promoting entry into and progression through mitosis?
Which cyclin is responsible for promoting entry into and progression through mitosis?
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Which CDK is associated with S-phase cyclins and is directly involved with DNA synthesis?
Which CDK is associated with S-phase cyclins and is directly involved with DNA synthesis?
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When do the levels of S-phase cyclins decline?
When do the levels of S-phase cyclins decline?
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Mitotic cyclin-CDK complexes are synthesized during S-phase and G2 phase, but their activity is held in check until what event?
Mitotic cyclin-CDK complexes are synthesized during S-phase and G2 phase, but their activity is held in check until what event?
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Which of the following is NOT a class of cyclins defined by their presence and activity during the cell cycle?
Which of the following is NOT a class of cyclins defined by their presence and activity during the cell cycle?
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What is the main purpose of the M/G1 checkpoint?
What is the main purpose of the M/G1 checkpoint?
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What are the two main classes of regulatory molecules that control cell cycle progression?
What are the two main classes of regulatory molecules that control cell cycle progression?
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Which cyclin is primarily responsible for coordinating the cell cycle with extracellular signals such as growth factors?
Which cyclin is primarily responsible for coordinating the cell cycle with extracellular signals such as growth factors?
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What is the role of the Cyclin E-CDK2 complex in the cell cycle?
What is the role of the Cyclin E-CDK2 complex in the cell cycle?
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If a cell does not pass a cell cycle checkpoint, what is the most likely outcome?
If a cell does not pass a cell cycle checkpoint, what is the most likely outcome?
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What is the significance of the START point in the cell cycle?
What is the significance of the START point in the cell cycle?
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Based on information in the text, which of the following is NOT directly regulated at the M/G1 checkpoint?
Based on information in the text, which of the following is NOT directly regulated at the M/G1 checkpoint?
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Which cyclin is known to accumulate during the late G1 phase of the cell cycle?
Which cyclin is known to accumulate during the late G1 phase of the cell cycle?
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What is the primary role of cyclins in cell cycle regulation?
What is the primary role of cyclins in cell cycle regulation?
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How can the activity of the cyclin-CDK complex be modulated?
How can the activity of the cyclin-CDK complex be modulated?
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What is a key function of the retinoblastoma protein (pRb) in the cell cycle?
What is a key function of the retinoblastoma protein (pRb) in the cell cycle?
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During which phase of the cell cycle would you expect to find cells with twice the DNA content of cells in G1?
During which phase of the cell cycle would you expect to find cells with twice the DNA content of cells in G1?
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What is the function of the E2F transcription factor family regulated by Rb?
What is the function of the E2F transcription factor family regulated by Rb?
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Which cellular structure is responsible for organizing the microtubules of the mitotic spindle?
Which cellular structure is responsible for organizing the microtubules of the mitotic spindle?
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What is the process by which the cyclin controlling a specific cell cycle phase is removed?
What is the process by which the cyclin controlling a specific cell cycle phase is removed?
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What is the main purpose of mitosis?
What is the main purpose of mitosis?
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During which phase of mitosis do the nuclear lamina and nuclear pore complexes disassemble?
During which phase of mitosis do the nuclear lamina and nuclear pore complexes disassemble?
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What is a common feature of cells deficient in RB function?
What is a common feature of cells deficient in RB function?
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What is the direct product of a primary spermatocyte in spermatogenesis?
What is the direct product of a primary spermatocyte in spermatogenesis?
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During oogenesis, at what stage are fetal oocytes arrested until ovulation?
During oogenesis, at what stage are fetal oocytes arrested until ovulation?
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Which cell type is considered a 'static cell' and is known for not undergoing division?
Which cell type is considered a 'static cell' and is known for not undergoing division?
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Which of the following cell types is classified as a ‘stable cell population’?
Which of the following cell types is classified as a ‘stable cell population’?
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Which cells are known for their rapid renewal rate?
Which cells are known for their rapid renewal rate?
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Which of the following is NOT a characteristic of renewing cell populations?
Which of the following is NOT a characteristic of renewing cell populations?
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What is a key difference between spermatogenesis and oogenesis?
What is a key difference between spermatogenesis and oogenesis?
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Where are the majority of human female future egg cells in the human body at birth?
Where are the majority of human female future egg cells in the human body at birth?
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Study Notes
Cell Cycle and Cell Division
- The cell cycle is a series of events that take place in a cell as it grows and divides.
- It's generally divided into two phases: interphase and mitosis.
- During interphase, the cell spends most of its time performing its unique functions.
- Mitosis is the phase of the cell cycle during which the cell divides into two daughter cells.
- Interphase consists of three distinctive phases: G1 (presynthesis), S (DNA replication), and G2 (post-DNA duplication).
- G0 is a resting state for some cells.
- There are three main checkpoints in the cell cycle: G₁/S, G₂/M, and M/G₁.
- Checkpoints ensure that the cell proceeds to the next phase only when the proper requirements of that phase are met.
- The cell cycle checkpoints are used by the cell to monitor and regulate the progress of the cell cycle.
- Cell cycle checkpoints are used by the cell to monitor and regulate the progress of the cell cycle.
Overview of Cell Cycle
- The cell cycle includes the process through which cells replicate and make two new cells.
Stages of Cell Cycle
- Cells spend most of their time in interphase during which they grow, replicate their chromosomes, and prepare for cell division.
- The cell then undergoes mitosis, and completes its division.
- The resulting cells are called daughter cells, and each enters their own interphase.
Cell Cycle Phases
- G₁ phase: The cell gathers nutrients and synthesizes RNA and proteins required for DNA synthesis and chromosome replication.
- S phase: DNA synthesis occurs, forming new chromatids. This phase takes about 7.5 to 10 hours. Replication starts at many sites along the chromosome called "replicons".
- G₂ Phase: The cell examines replicated DNA in preparation for cell division. Cell growth and cytoplasmic organelle reorganization can occur during this phase.
Cell Cycle Control
- The preparations of the cell are checked by regulatory molecules (proteins).
- Detection and repair of genetic damage are critical parts of cell cycle regulation.
- The cell cycle regulation involves two classes of proteins: Cyclins and Cyclin-dependent kinases (CDKs).
Cell Cycle Checkpoints: G1/S, G2/M, and M/G1
- G₁/S checkpoint: Checks for cell size, nutrients, DNA damage, and proper preparations for DNA replication.
- G₂/M checkpoint: Checks for proper DNA replication, all preparations required for the M phase, including tubulin synthesis. P53 regulates the progression through the G1 phase to ensure DNA damage can be repaired.
- M/G₁ checkpoint: Checks the assembly of mitotic spindles, prevents premature entry into anaphase, and checks the chromosome segregation. Checks whether the M phase cyclins and Cdk complex are activated to initiate mitosis.
Cyclins
- Cyclins are regulatory proteins that determine the activity of CDKs.
- There are four classes of cyclins: G₁ Cyclins (Cyclin D), G₁/S Cyclin (Cyclin E), the S-phase cyclins (Cyclins E and A), and M-phase cyclins (Cyclin B).
- The most important regulatory control is ubiquitination-mediated protein degradation.
CDKs
- CDKs (Cyclin-dependent kinases) are protein kinases.
- They play important roles, controlling cell division and mediating transcription responses to extra- and intracellular cues.
- A CDK binds a regulatory protein (cyclin) to become active.
- CDK activity is also modulated by phosphorylation and other binding proteins.
- CDKs are divided into sub-families linked to specific cell cycle stages.
Major Cyclin and Cyclin-dependent Kinase Complex Proteins
- There are examples of target proteins for cyclin complexes, including Phosphorylates Rb protein, which releases E2F. E2F is a transcription factor. E2F activation is critical for several G₁ activities. This complex also regulates many other proteins in the cell cycle.
Mitotic Catastrophe
- The improper distribution of chromosomes during mitosis can compromise cellular functions, reduce fitness or contribute to malignant transformation.
- Mitotic catastrophe is an onco-suppressive mechanism of cell death, it precedes apoptosis, necrosis or senescence, and plays an important role in cancer formation and progression.
- Some drugs (e.g., vinca alkaloids) can induce mitotic catastrophe by affecting microtubule functions.
Cell Division
- A crucial process for increasing cell numbers, tissue renewal, and wound repair.
Mitosis
- Mitosis is a form of cell division where replicated chromosomes and their genes are equally partitioned into two identical groups.
- Mitosis occurs in all somatic cells.
- Includes: Karyokinesis (division of the nucleus) and Cytokinesis (division of cytoplasm and organelles).
- Mitosis has 4 phases: Prophase, Metaphase, Anaphase, and Telophase.
Prophase
- The nucleolus disappears.
- Replicated chromatin condenses.
- Centrosomes and duplicated centrioles separate and organize the mitotic spindle.
- Lamins and inner nuclear membrane are phosphorylated.
Metaphase
- Chromosomes are condensed further.
- Chromosome alignment occurs at the metaphase plate.
- Microtubules move chromosomes into alignment.
Anaphase
- Sister chromatids separate.
- Moves towards opposite spindle poles.
- Microtubule motor proteins cause shortening of the microtubules.
Telophase
- The two sets of chromatids are at the spindle poles.
- Microtubules depolymerize.
- The nuclear envelope reassembles around the chromosomes.
- A cleavage furrow forms as actin filaments pull the membrane inward.
- The constriction leads to the final division.
Meiosis
- Meiosis is a specialized cell division that only occurs in germ cells to produce gametes (sperm and eggs).
- Meiosis results in four haploid cells that contain half the number of chromosomes as the parent cell.
- It involves two consecutive cell divisions (Meiosis I and Meiosis II), producing 4 genetically unique cells.
- Meiosis includes crossing over events that lead to unique combinations of genes.
Spermatogenesis
- The process of meiosis that produces four haploid sperm cells from one primary spermatocyte.
Oogenesis
- The process of meiosis that produces one haploid egg (Ovum) and three polar bodies.
- All primary oocytes (future eggs) are present at birth, arrested at prophase I.
Cell Renewal
- Static/Non-dividing cells: Do not divide (e.g., central nervous system cells).
- Stable cell populations (facultative mitotic cells): Divide regularly and slowly (e.g., cells in bone and cartilage).
- Renewing cell populations (labile cells): Divide frequently (e.g., blood cells).
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Description
Test your knowledge on the cell cycle and meiosis with this comprehensive quiz. Explore topics such as interphase, DNA replication, and the phases of meiosis. Challenge yourself to see how well you understand the key concepts involved in cell division.
