Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

3. Energy & Cell Processes

Interphase

Anatomy & Physiology

3. Energy & Cell Processes

Interphase

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2:04 minutes

Problem 9

Textbook Question

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 percentb. 50 percentc. 75 percentd. 100 percent

Verified step by step guidance

Step 1: Understand the cell cycle. The cell cycle consists of four main phases: G1, S, G2, and M. During the G1 phase, the cell grows and prepares for DNA replication. In the S phase, DNA replication occurs. In the G2 phase, the cell prepares for division, and in the M phase, the cell divides.

Step 2: Understand the pulse-chase experiment. In a pulse-chase experiment, a radioactive substance (in this case, thymidine) is added to a cell culture for a short period of time (the pulse). The radioactive substance is then removed and replaced with a non-radioactive substance (the chase). Cells that were in the S phase during the pulse will incorporate the radioactive thymidine into their DNA, and can be detected later.

Step 3: Calculate the total cell cycle time. The total cell cycle time is the sum of the times spent in each phase. In this case, it's 4 hours in G1 phase, 2 hours in S phase, 2 hours in G2 phase, and 30 minutes (or 0.5 hours) in M phase. Add these times together.

Step 4: Determine when cells would be radiolabeled. Cells would be radiolabeled if they were in the S phase during the pulse. Since the pulse was 9 hours ago, any cells that are currently in the M phase must have been in the S phase 9 hours ago. To find these cells, subtract 9 hours from the total cell cycle time.

Step 5: Calculate the percentage of radiolabeled cells. The percentage of radiolabeled cells is the number of cells that were in the S phase during the pulse (and are now in the M phase) divided by the total number of cells, multiplied by 100. Since all cells in the M phase were in the S phase during the pulse, the percentage of radiolabeled cells is the same as the percentage of cells in the M phase.

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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 these phases is crucial for determining how long cells spend in each stage and how this affects the timing of mitosis.

Pulse-Chase Experiment

A pulse-chase experiment involves exposing cells to a labeled compound (the pulse) for a short period, followed by a chase period where the labeled compound is removed. This technique helps track the incorporation of the label into cellular components over time. In this context, radioactive thymidine is used to label cells during DNA synthesis, allowing researchers to determine how many cells have incorporated the label by the time of observation.

Radiolabeling and Mitotic Cells

Radiolabeling refers to the incorporation of a radioactive isotope into a molecule, which can then be detected. In the context of the cell cycle, only cells that are in the S phase during the pulse will incorporate the radioactive thymidine. By calculating the time spent in each phase, one can determine the percentage of cells that will be mitotic and radiolabeled after a given time, which is essential for answering the question about the percentage of mitotic cells that would be radiolabeled after 9 hours.