Question

Suppose that a genetic alteration resulted in the synthesis of cyclin-dependent kinases that no
longer provided the "go" signal at the cellular checkpoint. Predict the immediate outcome if
this were to alter the normal cell life-cycle processes at the G1 checkpoint. The cells involved
would
(1 point)
grow and otherwise function undergoing mitosis
exit the cell cycle completely and enter a nondividing cellular state.
most likely remain in suspended metaphase, unable to enter anaphase.
proceed as normal and enter the G1, S, G2, and M phases and divide.

Answer 1

Cyclins depend on cylin dependent kinases to get activated. At the G1 phase or the restriction point where cells are "checked" to be appropriately sized and have sufficient energy reserves, growth dependent CDK activity is required for DNA replication and also to further initiate S phase. Therefore, if the cdks are not able to give the "go" signal, these cells would go into a resting phase or G0. Since in this case the gene has been altered to not give the go signal, therefore the cells will remain in G0 phase. The outcome of this in normal life cell processes would differ from cell type to cell type. For example, few cells like the heart cells remain in G0 phase for eternity at a certain point of maturity.