Final answer:
Checkpoint proteins, DNA damage response, and tumor suppressor genes are examples of internal factors that regulate cell division. Growth factors, crowding of cells, and neighboring cell death are examples of external factors that regulate cell division.
Step-by-step explanation:
Three examples of internal factors that regulate cell division are checkpoint proteins, such as cyclins and cyclin-dependent kinases (Cdks), which control the progression of the cell cycle. These proteins ensure that the cells are ready to move to the next stage of division. Another internal factor is DNA damage response, which can activate cell cycle arrest to allow for DNA repair before continuing with division. Lastly, tumor suppressor genes, like p53, help regulate cell division by inhibiting the growth and division of damaged cells.
External factors that regulate cell division include growth factors, such as human growth hormone (HGH), which stimulate cell division. Crowding of cells can also inhibit cell division due to lack of space and resources. Additionally, neighboring cells undergoing cell death can trigger nearby cells to divide and replace the lost cells.