Final answer:
The overexpression of cyclin D promotes the transition from the G1 phase to the S phase in the cell cycle, allowing the cell to move forward with DNA replication, not apoptosis or decreasing telomerase activity.
Step-by-step explanation:
The student is asking about the role of cyclin D overexpression in the cell cycle. Cyclin D, along with Cyclin-dependent kinase (Cdk), is a positive regulator molecule that facilitates the transition from one phase of the cell cycle to the next. Overexpression of cyclin D does not activate apoptosis or increase contact inhibition, nor does it decrease telomerase activity. Instead, cyclin D primarily functions to promote the transition from G1 to S phase in the cell cycle. This transition allows the cell to move forward with DNA replication.
Apoptosis, or programmed cell death, is regulated by different proteins, such as p53 and p21. These act as negative regulatory molecules, which can trigger apoptosis if vital cell cycle events do not occur, especially if there is damaged DNA or other forms of cellular stress. But cyclin D's role is the opposite, encouraging the cell to progress through the cycle rather than initiating cell death.
Therefore, the correct answer to the question, "Overexpression of cyclin D" is E. promotes transition from G1 to S phase.