AP BIOLOGY

Detailed explanation-1: -Loss of this function causes an identity crisis allowing G2 phase to overlap with S phase, leading to incomplete replication, an early mitosis, and subsequent DNA damage. Because the ATR-FOXM1 pathway ensures that G2 events are dependent on the completion of S phase, we refer to this as an intrinsic S/G2 checkpoint.

Detailed explanation-2: -The G2-phase checkpoint, also known as G2/M-phase checkpoint, has the function of preventing cells with damaged DNA, lasting from the G1 and S phases or generated in G2, from undergoing mitosis. The mechanisms acting during the G2-phase checkpoint converge on the inhibition of the mitotic complex CDK1-cyclin B.

Detailed explanation-3: -During S phase, any problems with DNA replication trigger a ‘’checkpoint”-a cascade of signaling events that puts the phase on hold until the problem is resolved. The S phase checkpoint operates like a surveillance camera; we will explore how this camera works on the molecular level.

Detailed explanation-4: -The G2 checkpoint ensures all of the chromosomes have been replicated and that the replicated DNA is not damaged before cell enters mitosis. The M checkpoint determines whether all the sister chromatids are correctly attached to the spindle microtubules before the cell enters the irreversible anaphase stage.