What is the main distinction between a spontaneous mutation and an induced mutation?

The main distinction between a spontaneous mutation and an induced mutation lies in the source of their occurrence. Induced mutations are specifically caused by external factors, such as chemical agents, radiation, or other environmental influences that directly alter the DNA sequence. This means that these types of mutations result from the impact of outside forces on the genetic material.

In contrast, spontaneous mutations occur naturally without any external influence, typically arising from errors during DNA replication or from inherent chemical processes within the cell. These mutations can happen during normal cellular processes and are often random in nature, independent of any environmental stress or external manipulation.

By understanding this distinction, it becomes clear that the correct answer emphasizes the role of external agents in inducing mutations, which is a fundamental concept in genetics and molecular biology, highlighting how different types of mutations arise in living organisms.