Cell cycle
56 flashcards covering Cell cycle for the MCAT Biology & Biochemistry section.
The cell cycle is the orderly sequence of events that a cell undergoes to grow, replicate its DNA, and divide into two daughter cells. This process is fundamental to life, enabling growth, tissue repair, and reproduction in organisms. It includes key phases: interphase, where the cell prepares by growing and duplicating its genetic material, and the mitotic phase, which involves actual division. Understanding the cell cycle helps explain how cells maintain proper function and how errors can lead to problems like uncontrolled growth.
On the MCAT, the cell cycle appears in biology and biochemistry questions, often as multiple-choice items testing phase sequences, regulatory mechanisms, or the consequences of disruptions. Common traps include confusing the sub-phases of interphase or overlooking checkpoints that prevent DNA damage. Focus on key concepts like the roles of cyclins, cyclin-dependent kinases, and external signals in regulation, as these are frequently emphasized. Remember to practice with diagrams to solidify your grasp of the stages.
Terms (56)
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Cell cycle
The cell cycle is the series of events that a eukaryotic cell undergoes as it grows and divides, typically divided into interphase and the mitotic phase.
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Interphase
Interphase is the longest phase of the cell cycle, during which the cell grows, performs its normal functions, and replicates its DNA, subdivided into G1, S, and G2.
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G1 phase
The G1 phase is the first gap phase in interphase where the cell grows and synthesizes proteins needed for DNA replication.
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S phase
The S phase is when DNA synthesis occurs, resulting in each chromosome being duplicated to produce two sister chromatids.
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G2 phase
The G2 phase is the second gap phase where the cell continues to grow and checks for DNA replication errors before entering mitosis.
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Mitotic phase
The mitotic phase is when the cell divides its nucleus and cytoplasm, consisting of mitosis and cytokinesis, to produce two daughter cells.
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Mitosis
Mitosis is the process of nuclear division that ensures each daughter cell receives an identical set of chromosomes, occurring in several stages.
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Prophase
Prophase is the first stage of mitosis where chromosomes condense, the nuclear envelope breaks down, and the mitotic spindle begins to form.
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Prometaphase
Prometaphase is when the nuclear envelope fragments, allowing microtubules to attach to kinetochores on the chromosomes.
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Metaphase
Metaphase is the stage where chromosomes align at the cell's equatorial plate, attached to microtubules from both centrosomes.
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Anaphase
Anaphase is when sister chromatids separate and are pulled to opposite poles of the cell by the shortening microtubules.
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Telophase
Telophase is the final stage of mitosis where chromosomes decondense, the nuclear envelope reforms, and the cell prepares for cytokinesis.
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Cytokinesis
Cytokinesis is the division of the cytoplasm following mitosis, resulting in two separate daughter cells with their own organelles.
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Checkpoints
Checkpoints are control mechanisms in the cell cycle that halt progression if conditions like DNA integrity or proper chromosome alignment are not met.
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G1 checkpoint
The G1 checkpoint ensures the cell is large enough and has no DNA damage before entering S phase, often regulated by growth factors and tumor suppressors.
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G2 checkpoint
The G2 checkpoint verifies that DNA replication is complete and accurate, preventing entry into mitosis if errors are detected.
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Spindle assembly checkpoint
The spindle assembly checkpoint, or M checkpoint, ensures all chromosomes are properly attached to the spindle before anaphase begins.
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Cyclins
Cyclins are proteins that regulate the cell cycle by binding to and activating cyclin-dependent kinases at specific phases.
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Cyclin-dependent kinases
Cyclin-dependent kinases are enzymes that, when bound to cyclins, phosphorylate target proteins to drive the cell through different phases.
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Maturation promoting factor
Maturation promoting factor is a complex of cyclin B and CDK1 that triggers entry into mitosis by phosphorylating key proteins.
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p53
p53 is a tumor suppressor protein that halts the cell cycle at the G1 checkpoint in response to DNA damage, allowing for repair or triggering apoptosis.
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Rb protein
The Rb protein regulates the G1 to S transition by binding and inhibiting transcription factors until it is phosphorylated by CDKs.
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E2F transcription factor
E2F is a transcription factor that promotes genes required for S phase when released from Rb protein inhibition.
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Anaphase-promoting complex
The anaphase-promoting complex is an E3 ubiquitin ligase that targets proteins for degradation, allowing sister chromatid separation.
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Kinetochore
The kinetochore is a protein structure on the centromere of a chromosome where microtubules of the mitotic spindle attach.
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Centrosome
The centrosome is the main microtubule-organizing center in animal cells, duplicating and helping form the mitotic spindle.
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Microtubules
Microtubules are dynamic cytoskeletal filaments that assemble into the mitotic spindle to separate chromosomes during cell division.
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Cohesins
Cohesins are proteins that hold sister chromatids together until anaphase, when they are cleaved to allow separation.
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Origin of replication
Origins of replication are specific DNA sequences where DNA synthesis begins during the S phase.
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Telomeres
Telomeres are protective caps at the ends of chromosomes that shorten with each cell division, potentially leading to cell cycle arrest.
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Telomerase
Telomerase is an enzyme that adds repetitive sequences to telomeres, maintaining chromosome length in cells like stem cells.
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Apoptosis
Apoptosis is programmed cell death that can be triggered if the cell cycle checkpoints detect irreparable damage.
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Growth factors
Growth factors are external signals that stimulate cell division by activating pathways that promote progression through the cell cycle.
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Restriction point
The restriction point in G1 is a critical decision point where the cell commits to divide, influenced by growth factors and nutrient availability.
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DNA damage response
The DNA damage response pathway senses and repairs DNA lesions, often leading to cell cycle arrest at checkpoints.
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Cell cycle arrest
Cell cycle arrest is a temporary or permanent halt in progression, such as in response to DNA damage, to prevent propagation of errors.
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Quiescent cells
Quiescent cells enter a non-dividing G0 phase, exiting the cell cycle until stimulated by signals to re-enter.
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Binary fission
Binary fission is the asexual reproduction process in prokaryotes, contrasting with the eukaryotic cell cycle by lacking mitosis.
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Oncogenes
Oncogenes are mutated genes that promote uncontrolled cell cycle progression, contributing to cancer development.
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Tumor suppressors
Tumor suppressors are genes that inhibit the cell cycle or promote apoptosis, preventing uncontrolled cell growth.
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Senescence
Senescence is a state of permanent cell cycle arrest that occurs in response to stress or telomere shortening, limiting cell proliferation.
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Flow cytometry
Flow cytometry is a technique used to analyze the cell cycle by measuring DNA content in a population of cells.
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Cleavage furrow
The cleavage furrow is the indentation in animal cells where the cell membrane pinches inward during cytokinesis.
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Cell plate
The cell plate is a structure formed in plant cells during cytokinesis that develops into a new cell wall between daughter cells.
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Ploidy
Ploidy refers to the number of chromosome sets in a cell, which the cell cycle maintains as diploid in most somatic cells.
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Astral microtubules
Astral microtubules extend from centrosomes to the cell cortex, aiding in spindle positioning and cytokinesis.
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Kinetochore microtubules
Kinetochore microtubules connect to chromosomes and pull them apart during anaphase of mitosis.
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Interpolar microtubules
Interpolar microtubules overlap at the spindle equator and help push the poles apart during anaphase.
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Replication licensing
Replication licensing ensures DNA is replicated only once per cell cycle by assembling pre-replication complexes at origins.
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Signal transduction
Signal transduction pathways relay external signals to the cell cycle machinery, often through phosphorylation cascades.
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Chemotherapy targets
Chemotherapy targets rapidly dividing cells by interfering with DNA replication or spindle formation in the cell cycle.
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Cell cycle length
Cell cycle length varies by cell type, typically 24 hours in mammalian cells, with interphase being the longest part.
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Condensins
Condensins are proteins that help compact chromosomes during prophase, making them suitable for segregation.
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Ubiquitination
Ubiquitination marks proteins for degradation in the cell cycle, such as securin to allow anaphase progression.
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Meiosis comparison
Meiosis is a specialized cell cycle for gamete formation, involving two divisions to reduce chromosome number, unlike mitosis.
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Cyclin degradation
Cyclin degradation at the end of each phase resets the cell cycle by inactivating CDKs through ubiquitin-mediated proteolysis.