Select the Characteristics That are True of Restriction Points

Question

Select the characteristics that are true of restriction points.Check all that apply.
A) An example is the boundary between G₁ and S phase.
B) In many cases molecular changes must be present at this point for the cell to continue through the cell cycle.
C) Cells passing this point are committed to the next stage of the cell cycle.
D) Cells passing this point can reverse to an earlier phase of the cell cycle.

Accepted Answer

Restriction points are specific points in the cell cycle where the progression of the cycle is regulated. An example of a restriction point is the G₁/S checkpoint, which marks the boundary between G₁ and S phase. At this point, the cell must make a decision about whether to continue through the cell cycle or to exit the cycle and enter a quiescent state. Molecular changes, such as the activation of cyclin-dependent kinases (CDKs), often need to be present for the cell to pass through the restriction point. Once a cell passes a restriction point, it is committed to the next stage of the cell cycle, and cannot reverse to an earlier phase. Therefore, options A, B, and C are true for restriction points. Option D is incorrect because cells passing a restriction point cannot reverse to an earlier phase of the cell cycle.