What is the primary role of tumor suppressor genes in cell regulation?

Tumor suppressor genes play a crucial role in regulating the cell cycle and preventing the uncontrolled growth of cells, which is a hallmark of cancer. One of their primary functions is to signal when a cell should undergo apoptosis, or programmed cell death. This is important because it ensures that damaged or potentially cancerous cells are eliminated from the body.

When tumor suppressor genes are functional, they produce proteins that can inhibit cell division, repair DNA mistakes, or initiate apoptosis when necessary. By controlling cell death, these genes help maintain tissue integrity and prevent the accumulation of cells that may lead to tumorigenesis.

In contrast, the other options relate to different aspects of cellular activity. While some genes do tell cells when to grow or act as promoters of cell division, these functions are typically attributed to oncogenes rather than tumor suppressor genes. Initiating DNA replication is a separate function that involves various genes and proteins not classified as tumor suppressors. Therefore, the most accurate representation of the primary role of tumor suppressor genes is their involvement in regulating cell death, making the answer clear and supported by the biological functions of these critical genetic elements.