Which of the following describes proto-oncogenes?

Proto-oncogenes are normal genes that play essential roles in regulating cell growth and division. When these genes are altered due to mutations, changes in expression, or amplification, they can become oncogenes, which contribute to the uncontrolled cell proliferation characteristic of cancer. This transformation usually occurs through various mechanisms, such as point mutations, gene amplifications, or chromosomal rearrangements.

In contrast, the other descriptions do not accurately reflect proto-oncogenes. For instance, they do not inherently cause cancer without modification, as they are typically involved in normal cellular processes until their function is altered. Additionally, they are not specifically tumor-suppressing genes, which would be categorized as tumor suppressor genes instead. Lastly, proto-oncogenes have a significant impact on the cell cycle and cell signaling pathways, making their disruption a key factor in cancer development. Hence, the defining characteristic of proto-oncogenes is their potential to become oncogenes through alterations, which aligns with the correct choice.