Textbook Question
Identify at least two events in the cell cycle that must be completed successfully for daughter cells to share an identical complement of chromosomes.
Ch. 12 - The Cell Cycle
Freeman8th EditionBiological ScienceISBN: 9780138276263
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Table of contents
- Ch. 1 - Biology: The Study of Life13
- Ch. 2 - Water and Carbon: The Chemical Basis of Life14
- Ch.3 - Protein Structure and Function10
- Ch.4 - Nucleic Acids and the RNA World10
- Ch. 5 - An Introduction to Carbohydrates10
- Ch. 6 - Lipids, Membranes, and the First Cells11
- Ch. 7 - Inside the Cell10
- Ch. 8 - Energy and Enzymes: An Introduction to Metabolism10
- Ch. 9 - Cellular Respiration and Fermentation11
- Ch. 10 - Photosynthesis12
- Ch. 11 - Cell-Cell Interactions12
- Ch. 12 - The Cell Cycle8
- Ch. 13 - Meiosis12
- Ch. 14 - Mendel and the Gene23
- Ch. 15 - DNA and the Gene: Synthesis and Repair15
- Ch. 16 - How Genes Work16
- Ch. 17 - Transcription, RNA Processing, and Translation16
- Ch. 18 - Control of Gene Expression in Bacteria16
- Ch. 19 - Control of Gene Expression in Eukaryotes12
- Ch. 20 - The Molecular Revolution: Biotechnology, Genomics, and New Frontiers15
- Ch. 21 - Genes, Development, and Evolution12
- Ch. 22 - Evolution by Natural Selection16
- Ch. 23 - Evolutionary Processes13
- Ch. 24 - Speciation15
- Ch. 25 - Phylogenies and the History of Life13
- Ch. 26 - Bacteria and Archaea15
- Ch. 27 - Diversification of Eukaryotes16
- Ch. 28 - Green Algae and Land Plants16
- Ch. 29 - Fungi18
- Ch. 30 - An Introduction to Animals9
- Ch. 31 - Protostome Animals15
- Ch. 32 - Deuterostome Animals17
- Ch. 33 - Viruses16
- Ch. 34 - Plant Form and Function16
- Ch. 35 - Water and Sugar Transport in Plants16
- Ch. 36 - Plant Nutrition13
- Ch. 37 - Plant Sensory Systems, Signals, and Responses16
- Ch. 38 - Flowering Plant Reproduction and Development16
- Ch. 39 - Animal Form and Function17
- Ch. 40 - Water and Electrolyte Balance in Animals16
- Ch. 41 - Animal Nutrition16
- Ch. 42 - Gas Exchange and Circulation16
- Ch. 43 - Animal Nervous Systems16
- Ch. 44 - Animal Sensory Systems16
- Ch. 45 - Animal Movement11
- Ch. 46 - Chemical Signals in Animals16
- Ch. 47 - Animal Reproduction and Development16
- Ch. 48 - The Immune System in Animals16
- Ch. 49 - An Introduction to Ecology15
- Ch. 50 - Behavioral Ecology16
- Ch. 51 - Population Ecology16
- Ch. 52 - Community Ecology20
- Ch. 53 - Ecosystems and Global Ecology17
- Ch. 54 - Biodiversity and Conservation Ecology18
Chapter 12, Problem 9
A particular cell type spends 4 hours in G1 phase, 2 hours in S-phase, 2 hours in G2 phase, and 30 minutes in M-phase. If a pulse-chase experiment were performed with radioactive thymidine on an asynchronous culture of such cells, what percentage of mitotic cells would be radiolabeled 9 hours after the pulse?
a. 0 percent
b. 50 percent
c. 75 percent
d. 100 percent
Verified step by step guidance1
Understand the problem: The question involves a pulse-chase experiment with radioactive thymidine, which labels DNA during the S phase. The goal is to determine the percentage of mitotic cells that would be radiolabeled 9 hours after the pulse. This requires understanding the cell cycle and the timing of each phase.
Calculate the total duration of the cell cycle: Add the durations of all phases (G1, S, G2, and M). The total cell cycle time is: \(4 \text{ hours (G1)} + 2 \text{ hours (S)} + 2 \text{ hours (G2)} + 0.5 \text{ hours (M)} = 8.5 \text{ hours}\).
Determine the time elapsed since the pulse relative to the cell cycle: After 9 hours, the cells have completed one full cycle (8.5 hours) and have entered the next cycle. Subtract the total cell cycle time from the elapsed time: \(9 \text{ hours} - 8.5 \text{ hours} = 0.5 \text{ hours}\). This means the cells are 0.5 hours into their second cycle.
Identify the phase of radiolabeled cells: Radiolabeled cells are those that were in the S phase during the pulse. These cells will progress through G2, M, and G1 before entering the next M phase. Calculate the time it takes for these cells to reach M phase: \(2 \text{ hours (G2)} + 0.5 \text{ hours (M)} + 4 \text{ hours (G1)} = 6.5 \text{ hours}\). Adding this to the 2 hours spent in S phase, radiolabeled cells will reach M phase \(2 + 6.5 = 8.5 \text{ hours}\) after the pulse.
Determine the percentage of mitotic cells that are radiolabeled: At 9 hours, the radiolabeled cells have already reached M phase, and the culture is asynchronous. Since the cell cycle is continuous and the timing aligns, all mitotic cells at this point will be radiolabeled. Thus, the percentage of radiolabeled mitotic cells is 100%.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Cell Cycle Phases
The cell cycle consists of several phases: G1 (gap 1), S (synthesis), G2 (gap 2), and M (mitosis). Each phase has a specific duration and function, with G1 preparing the cell for DNA synthesis, S phase involving DNA replication, G2 preparing for mitosis, and M phase being the actual division of the cell. Understanding the timing of these phases is crucial for predicting how many cells will be in mitosis at a given time.
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Phases of The Krebs Cycle
Pulse-Chase Experiment
A pulse-chase experiment involves exposing cells to a labeled compound (the pulse) for a short time, followed by a period without the label (the chase). This technique allows researchers to track the incorporation of the label into cellular components over time. In this context, radioactive thymidine is used to label cells in the S phase, and the timing of the chase helps determine how many cells have progressed to mitosis.
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Asynchronous Cell Culture
An asynchronous cell culture contains cells at various stages of the cell cycle, rather than all being synchronized in the same phase. This diversity is important for understanding the overall behavior of a population of cells. In the context of the question, it means that at the time of the pulse-chase experiment, some cells will be in different phases, affecting the percentage of mitotic cells that become radiolabeled after a specific time.
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Related Practice
Textbook Question
What evidence suggests that during anaphase, kinetochore microtubules shorten at the kinetochore?
Textbook Question
Compare and contrast the effects of removing growth factors from asynchronous cultures of human cells that are normal and those that are cancerous.
Textbook Question
When a fruit fly embryo first begins to develop, a large cell is generated that contains over 8000 genetically identical nuclei. What is most likely responsible for this result?