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How do stable cells behave differently in response to stimuli compared to labile and permanent cells?
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Stable cells can be stimulated to re-enter the cell cycle, unlike labile cells that continuously cycle and permanent cells that do not re-enter once they have exited.
What are the main purposes of the cell cycle?
The main purposes are to replicate cells to produce two identical diploid cells and to control cell growth.
How do checkpoints ensure the accuracy of the cell cycle?
Checkpoints such as G1/S, G2/M, and metaphase ensure that the cell only proceeds to the next phase if conditions are optimal and DNA integrity is maintained.
What characterizes the G1 phase of interphase?
In the G1 phase, cells increase the number of organelles, synthesize proteins and enzymes necessary for DNA replication, and repair thymine dimers. Most cells reside in this phase.
What is checked at the G1/S checkpoint and why is it important?
The G1/S checkpoint ensures DNA integrity before replication, crucial to prevent passing on mutations to daughter cells.
How do motor proteins facilitate chromosome movement in anaphase?
Motor proteins like dynein and kinesin help in the movement of sister chromatids to opposite poles by interacting with microtubules.
Describe the roles of DNA polymerase types 1 and 3 in DNA replication.
DNA polymerase type 3 synthesizes new DNA strands, whereas type 1 replaces RNA primers with DNA nucleotides and proofreads the newly synthesized DNA.
Explain the semi-conservative model of DNA replication occurring during the S phase.
In the semi-conservative model, each daughter DNA molecule consists of one original (parental) strand and one newly synthesized strand.
What changes occur during prophase of mitosis?
During prophase, chromatin condenses into chromosomes, the nuclear envelope dissolves, and microtubule organizing centers, or centrioles, form.
What is the significance of chromatin condensation in mitosis?
Chromatin condensation is significant as it forms visible chromosomes, making it easier for the cell to ensure equal distribution of genetic material between daughter cells during mitosis.
How do aging cells exhibit changes in their ability to cycle?
Aging cells show telomere shortening, leading to senescence, and have reduced ability to re-enter the cell cycle, especially in permanent cell types.
How do labile, stable, and permanent cells differ in their behavior in the cell cycle?
Labile cells constantly cycle (e.g., skin, GI tract), stable cells enter the cycle when stimulated (e.g., liver), and permanent cells do not re-enter the cycle (e.g., neurons).
What is cytokinesis and which phase of mitosis does it occur in?
Cytokinesis is the physical separation of the cytoplasm into two daughter cells, occurring at the end of telophase.
What happens to the nuclear envelope during telophase?
During telophase, the nuclear envelope re-forms around the separated sets of chromosomes at each pole.
What are the potential outcomes of errors in the cell cycle checkpoints?
Errors can lead to uncontrolled cell growth, mutations, and potentially cancerous developments if checkpoints fail to correct errors in DNA replication or damage.
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