What are two factors that regulate the timing of the cell cycle?

Cyclins and regulatory proteins. Regulatory proteins include internal regulators and external regulators.

any of a number of proteins associated with the cycle of cell division which are thought to initiate certain processes of mitosis.

egulatory protein. regulatory protein (gene-regulatory protein) Any protein that influences the regions of a DNA molecule that are transcribed by RNA polymeraseduring the process of transcription. These proteins, which include transcriptionfactors, therefore help control the synthesis of proteins in cells.

the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to test the hypothesis, and development of a conclusion that confirms, rejects, or modifies the hypothesis.