between two thymine molecules. The resulting dimer is very stable. Although they can be removed through excision repairs, when UV damage is extensive, the entire DNA molecule breaks down and the cell dies. If the damage is not too extensive, precancerous or cancerous cells are created from healthy cells. Chemotherapy drugs Chemotherapeutics, by design, induce DNA damage and are targeted towards rapidly dividing cancer cells. However, these drugs can not tell the difference between sick and healthy cells, resulting in the damage of normal cells. Alkylating agents Alkylating agents are a type of chemotherapeutic drug which keeps the cell from undergoing mitosis by damaging its DNA. They work in all phases of the cell cycle. The use of alkylating agents may result in leukemia due to them being able to target the cells of the bone marrow. Cancer causing agents Carcinogens are known to cause a number of DNA lesions, such as single-strand breaks, double- strand breaks, and covalently bound chemical DNA adducts. Tobacco products are one of the most prevalent cancer-causing agents of today. Other DNA damaging, cancer-causing agents include asbestos, which can cause damage through physical interaction with DNA or by indirectly setting off a reactive oxygen species, excessive nickel exposure, which can repress the DNA damage-repair pathways, aflatoxins, which are found in food, and many more. Lesions of Nucleic Acids Oxidative lesions Oxidative lesions are an umbrella category of lesions caused by reactive oxygen species (ROS), reactive nitrogen species (RNS), other byproducts of cellular metabolism, and exogenous factors such as ionizing or ultraviolet radiation. Byproducts of oxidative respiration are the main source of reactive species which cause a background level of oxidative lesions in the cell. DNA and RNA are both affected by this, and it has been found that RNA oxidative lesions are more abundant in humans compared to DNA. This may be due cytoplasmic RNA having closer proximity to the electron transport chain. Known oxidative lesions characterized in DNA and RNA are many in number, as oxidized products are unstable and may resolve quickly. The hydroxyl radical and singlet oxygen are common reactive oxygen species responsible for these lesions. 8-oxo-guanine (8-oxoG) is the most abundant and well characterized oxidative lesion, found in both RNA and DNA. Accumulation of 8-oxoG may cause dire damage within the mitochondria and is thought to be a key player in the aging process. RNA oxidation has direct consequences in the