The Cell Cycle

The cell cycle is a process in which a cell first duplicates its genetic information and then divides to give rise to two daughter cells. To avoid mis-segregation of the genetic materials and incorporation of errors in the genome, the cell cycle is carefully monitored. This is achieved by positioning throughout the cell cycle a number of checkpoints designed to detect DNA damage, misaligned chromosomes, and incompletely replicated DNA. Checkpoints are mediated by cyclin-dependent kinase inhibitors (CKIs) in interphase and mitosis. On the other hand, progression through the cell cycle requires the combination of cyclins and cyclin-dependent kinases (CDKs), together of which regulate activities of target proteins by phosphorylation. The proper regulation of the cell cycle is critically important for cell proliferation as mutations in genes involved in cell cycle control often lead to cancer. This chapter reviews the components of the cell cycle and its control, checkpoint mechanisms, and provide examples of pathological consequences of dysregulation of the cell cycle machinery. This information is crucial for understanding the mechanisms regulating growth, proliferation, and differentiation of cells in the gastrointestinal tract.