If cyclin was always available in the cell at high concentrations, what affect would this have on the cell cycle?

Cells will progress through mitosis even when they are not ready.

Explanation:

Being a protein, cyclin controls the progression of cell in the cell cycle, when its concentration will be more it activates cyclin dependent kinase enzyme which are necessary in the synthesis of cell, hence mitosis occurs even when it is completely not ready for it. In this condition cytokinesis will not occur and hence mitosis will occur in which the cell will divide with more than one nucleus. This type of cells are called multinucleated cell.