Answer:
CDK
Step-by-step explanation:
If DNA is damaged or incompletely replicated in S phase, the inhibition of cyclin-dependent kinase (CDK) prevents the cell from entering M phase.
During S phase, the DNA of a cell is replicated in preparation for cell division. If this replication is incomplete or if the DNA is damaged, it can lead to problems with the cell's ability to divide properly. In such cases, the cell will not be able to enter M phase, which is the phase of the cell cycle in which the cell divides into two daughter cells.
One of the key molecules that controls the transition from S phase to M phase is cyclin-dependent kinase (CDK). CDK is an enzyme that plays a critical role in the regulation of the cell cycle. It is activated by a protein called cyclin, which is produced during S phase.
When DNA is damaged or incompletely replicated in S phase, the levels of cyclin are likely to be reduced. This, in turn, can lead to the inhibition of CDK, preventing the cell from entering M phase. As a result, the cell will not be able to divide properly, and this can have serious consequences for the health of the organism.
In summary, if DNA is damaged or incompletely replicated in S phase, the inhibition of CDK can prevent the cell from entering M phase. This helps to protect the organism from the potential harmful effects of damaged or incompletely replicated DNA.