Chapter 19: Problem 4

Where are the major regulatory points in the cell cycle?

Short Answer

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Answer: The major regulatory points in the cell cycle are the G1 checkpoint, the G2 checkpoint, and the M checkpoint. These checkpoints are crucial for monitoring the cell's progress through the cell cycle, preventing errors, and maintaining accurate cell division. They ensure that the cell is healthy, has sufficient resources, and that DNA replication and chromosome segregation are properly carried out. This prevents complications such as aneuploidy, which could lead to cancer or other cellular abnormalities.

Step by step solution

Understand the phases of the cell cycle

The cell cycle is composed of four main phases: G1 (the first gap phase), S (the synthesis phase), G2 (the second gap phase), and M (the mitosis phase). The G1 phase is the period when a cell is 'growing' and preparing for DNA replication, which occurs during the S phase. After DNA replication, the cell enters the G2 phase, where it prepares for mitosis, which occurs during the M phase. Mitosis is followed by cytokinesis, which divides the cell into two daughter cells.

Identify the first regulatory point - G1 checkpoint

The G1 checkpoint (also known as the restriction point or start checkpoint) is the first major regulatory point in the cell cycle. This checkpoint controls whether the cell will enter the S phase and replicate its DNA. If the cell is healthy and has sufficient energy and nutrients, it will continue to the S phase. If not, it will exit the cycle and enter a quiescent state known as G0, during which it may either become terminally differentiated or return to the cell cycle depending on specific signals.

Recognize the second regulatory point - G2 checkpoint

The second major regulatory point, the G2 checkpoint, determines whether the cell will proceed with mitosis. Before entering the M phase, the cell checks to ensure the DNA has been completely and accurately replicated during the S phase. If any errors or damage are found, the cell will attempt to repair the DNA before proceeding with mitosis.

Understand the final regulatory point - M checkpoint (Spindle Assembly Checkpoint)

The M checkpoint, also known as the spindle assembly checkpoint, occurs during mitosis and ensures that sister chromatids are correctly attached to spindle fibers before the cell proceeds to anaphase. This checkpoint ensures the proper segregation of chromosomes into the two daughter cells, preventing potential errors that could lead to aneuploidy (an abnormal number of chromosomes), a common hallmark of cancer cells. In summary, the major regulatory points in the cell cycle are the G1 checkpoint, the G2 checkpoint, and the M checkpoint. These checkpoints are essential for preventing errors and maintaining proper cell division.

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Where are the major regulatory points in the cell cycle?

Short Answer

Step by step solution

Understand the phases of the cell cycle

Identify the first regulatory point - G1 checkpoint

Recognize the second regulatory point - G2 checkpoint

Understand the final regulatory point - M checkpoint (Spindle Assembly Checkpoint)

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