What factor affects the lethal damage caused to DNA in irradiated cells?

The lethal damage caused to DNA in irradiated cells is influenced by multiple factors, each playing a significant role in the effectiveness of radiation therapy and cellular response to radiation.

Energy levels of radiation are crucial, as higher energy radiation typically leads to more severe damage due to increased ionization and excitation of atoms within the DNA structure. When radiation interacts with biological tissue, it can create free radicals and other reactive species, which can subsequently induce various types of DNA damage, such as single and double-strand breaks. Therefore, understanding the energy levels helps in predicting the extent of biological damage.

The type of radiation used is also a significant factor. Different types of radiation (e.g., alpha particles, beta particles, gamma rays, and X-rays) have distinct physical properties and biological effects. For instance, alpha particles have a high mass and charge, resulting in more densely ionizing interactions over a short path, causing more localized damage compared to gamma rays, which are less ionizing and penetrate deeper but may inflict less localized damage.

The presence of oxygen further influences the lethality of radiation damage. Cells exposed to oxygen while irradiated typically experience more damage due to the formation of reactive oxygen species, which can interact with DNA and enhance the likelihood of lethal hits.