A) A cell contains DNA damage that causes it to undergo apoptosis before reaching mitosis. This cell had twice the amount of DNA for a cell of
this type. During which checkpoint did this cell trigger apoptosis? (1 point)
G Checkpoint 1
G Checkpoint 2
M Checkpoint
No checkpoint meets these criteria.
No checkpoint meets these criteria.
In this scenario, the cell underwent apoptosis before reaching mitosis due to DNA damage. The fact that the cell had twice the amount of DNA for a cell of this type indicates that the DNA replication phase (S phase) occurred successfully.
During the cell cycle, there are three main checkpoints: G1 checkpoint, G2 checkpoint, and M checkpoint. These checkpoints serve as control mechanisms to ensure the proper progression and integrity of the cell cycle.
Given that the cell had already replicated its DNA and had twice the amount of DNA, we can rule out the G1 checkpoint as a possible trigger for apoptosis. This leaves us with the G2 checkpoint and the M checkpoint.
The G2 checkpoint occurs after DNA replication, where the cell checks for any DNA damage or errors before entering mitosis. If any issues are detected, the checkpoint can trigger apoptosis to prevent the replication of damaged DNA.
Therefore, to answer the question, the cell triggered apoptosis during the G2 checkpoint.
To determine at which checkpoint the cell triggered apoptosis, we need to consider the cell cycle stages and their associated checkpoints.
The cell cycle consists of several stages: G1 (Gap 1), S (Synthesis), G2 (Gap 2), and M (Mitosis). During cell cycle progression, there are three main checkpoints – G1 checkpoint, G2 checkpoint, and M checkpoint – where the cell assesses various conditions before proceeding to the next stage.
Given that the cell had twice the amount of DNA for a cell of this type, it suggests that the DNA replication during the S phase was completed, resulting in a doubled DNA content. However, since the cell underwent apoptosis before reaching mitosis, we need to identify which checkpoint would detect this DNA damage and trigger apoptosis.
The G1 checkpoint, also known as the restriction point, monitors DNA integrity and cellular environment, ensuring that the cell is ready for DNA synthesis during the S phase. If DNA damage is detected at this checkpoint, the cell can arrest the cell cycle, initiate DNA repair mechanisms, or undergo apoptosis if the damage is severe and irreparable.
The G2 checkpoint operates just before the cell enters the M phase. It checks for DNA damage and ensures that DNA replication has occurred correctly during the S phase. If damage is detected, the cell cycle can be halted for repair or can trigger apoptosis.
The M checkpoint, also called the spindle checkpoint, occurs during mitosis. It checks for proper chromosome attachment to spindle fibers and ensures that all chromosomes are aligned correctly before cell division proceeds. Any irregularities detected at this checkpoint can halt mitosis or induce apoptosis.
Based on the given information, it is unlikely that the G1 checkpoint triggered apoptosis, as the cell had already undergone DNA replication (S phase). The M checkpoint also seems unlikely, as the cell did not progress to mitosis. Thus, the most probable checkpoint at which this cell triggered apoptosis is the G2 checkpoint, detecting the DNA damage and initiating apoptosis before entering the M phase.
Therefore, the correct answer is G Checkpoint 2 (G2 checkpoint), as this is the checkpoint where the cell likely triggered apoptosis due to DNA damage.