CDKN1A is a gene that provides instructions for making a protein called p21. This protein plays a crucial role in regulating the cell cycle, which is the process that cells go through to grow and divide. By inhibiting certain proteins that promote cell division, p21 helps to control cell growth and prevent uncontrolled proliferation, which can lead to cancer. The expression of CDKN1A is often increased in response to DNA damage or stress, acting as a protective mechanism for cells. This gene is also associated with various biological processes, including aging and the response to different types of cellular stress, highlighting its importance in maintaining cellular health.