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Multiple Choice
During the cell cycle, what does the G$_1$ checkpoint primarily assess before allowing the cell to proceed to the S phase?
A
If the chromosomes are properly attached to the spindle fibers
B
Whether DNA replication has been completed successfully
C
Whether the cell has sufficient nutrients and proper DNA integrity
D
If the nuclear envelope has broken down
Verified step by step guidance
1
Understand the role of the G$_1$ checkpoint in the cell cycle: The G$_1$ checkpoint is a critical control point that determines whether a cell is ready to proceed to the S phase, where DNA replication occurs.
Identify the key factors assessed at the G$_1$ checkpoint: The checkpoint primarily evaluates whether the cell has sufficient nutrients to support growth and division, and whether the DNA is intact and free of damage.
Eliminate incorrect options: For example, assessing whether chromosomes are attached to spindle fibers is a function of the M checkpoint, not the G$_1$ checkpoint. Similarly, checking if DNA replication has been completed successfully occurs at the G$_2$ checkpoint.
Focus on the correct answer: The G$_1$ checkpoint ensures that the cell has adequate resources (nutrients) and that its DNA integrity is maintained before proceeding to the S phase.
Conclude the importance of the G$_1$ checkpoint: This checkpoint prevents cells with damaged DNA or insufficient resources from entering the S phase, thereby maintaining genomic stability and proper cell function.