Final answer:
A mutated gene can be the result of cellular damage from environmental agents like radiation, leading to DNA strand breaks and potential cancer if the cell's repair mechanisms, such as those involving the p53 protein, are compromised. This can happen due to environmental exposures and can increase cancer risk.
Step-by-step explanation:
A gene that is marked by cellular damage from an environmental agent such as radiation is often referred to as a mutated gene. Ionizing radiation, like that from radioactive decay or cosmic rays, can cause breaks in DNA strands, which can be particularly damaging to cells. Cells may react differently to this damage: they can attempt to repair the DNA, they can enter a state of dormancy, or they can initiate cell death if the damage is beyond repair. Mutations in DNA repair genes, such as the p53 gene, are common in cancer cells. This protein plays a significant role in the G1 checkpoint of the cell cycle, halting the cycle to allow for DNA repair or activating genes that can initiate cell death if repair is not possible. However, when the p53 gene is damaged, it loses its ability to control cell division and prevent the propagation of mutations, which can lead to cancer.
Environmental risk factors, including exposure to radiation from various sources, and other behaviors such as smoking, can increase the rate of DNA damage. This damage can lead to mutations if the DNA is replicated before repair, which can then be passed on to daughter cells. The integrity of genetic information is thus compromised, potentially leading to uncontrolled cell division and tumor formation.