What factors cause DNA damage?
DNA can be damaged by many different sorts of mutagens, which change the DNA sequence. Mutagens include oxidizing agents, alkylating agents and also high-energy electromagnetic radiation such as ultraviolet light and X-rays. The type of DNA damage produced depends on the type of mutagen. For example, UV light can damage DNA by producing thymine dimers, which are cross-links between pyrimidine bases. On the other hand, oxidants such as free radicals or hydrogen peroxide produce multiple forms of damage, including base modifications, particularly of guanosine, and double-strand breaks. In each human cell, about 500 bases suffer oxidative damage per day. Of these oxidative lesions, the most dangerous are double-strand breaks, as these are difficult to repair and can produce point mutations, insertions and deletions from the DNA sequence, as well as chromosomal translocations. Many mutagens fit into the space between two adjacent base pairs, this is called intercalating. Most intercalators are aromatic and planar molecules, and include Ethidium bromide, daunomycin, and doxorubicin. In order for an intercalator to fit between base pairs, the bases must separate, distorting the DNA strands by unwinding of the double helix. This inhibits both transcription and DNA replication, causing toxicity and mutations. As a result, DNA intercalators are often carcinogens, and benzopyrene diol epoxide, acridines, aflatoxin and ethidium bromide are well-known examples
What are some examples of mutagens?
Mutagens may be of physical, chemical or biological origin. They may act directly on the DNA, causing direct damage to the DNA, and most often result in replication error, or mutationsRadiation based mutagens (Wikipedia)Ionizing radiations such as X-rays, gamma rays and alpha particles may cause DNA breakage and other damages. The most common sources include cobalt-60 and cesium-137.Ultraviolet radiations with wavelength above 260 nm are absorbed strongly by bases, producing pyrimidine dimers, which can cause error in replication if left uncorrected.Radioactive decay, such as 14C in DNA which decays into nitrogenBiological Mutagens (Horticulture classes in college)Horticulturists achieve a specific mutation in plant cuttings with the application of colchicine, to the reproductive parts of the flowers. Colchicine is an extract from plants of the Autumn crocus. The mutation which occurs is to double the number of chromosomes, which results in plant with parts twice as large as normal. In this way a plain wild flower can be turned into a showy flower twice as large as the original.Another biological mutagen is simply aging of the egg or sperm. Damage to DNA in both plants and animals causes mutations, such as mongoloidism in humans when the egg has begun to deteriorate from age. Chemical Mutagens from an article by Gary Roberts, with Timothy Paustian, University of Wisconins-Madison ©2000Chemical mutagens are compounds that increase the frequency of some types of mutation. Among them are alkylators, including ethyl methane sulfonate (EMS), methyl methane sulfonate (MMS), diethylsulfate (DES), and nitrosoguanidine which tend to de-acidify the acidic properties of DNA. They also have the property of inducing error-prone DNA repair. This stimulation of error-prone repair allows all sorts of mutation types to occur. Nitrous Oxide can also cause mutations in the DNA affecting protein synthesis.
How does radiation both treat and cause cancer?
The biological effect of ionizing radiation is, in the doses we’re talking about, mediated by free oxygen radicals. The gamma rays hit oxygen atoms, knocking off an outer electron , which turns them into highly reactive oxygen ions that wreak havoc on most molecules including DNA. This introduces mutations that can cause cancer.For the treatment part, radiotherapy uses the fact that cancer cells are more brittle and less capable of repairing damage than normal cells. Normal cells have an intact DNA repair machinery which is engaged after radiation exposure, and either manages to fix the damage or trigger an orderly autodestruct mechanism. Cancerous cells have deficiencies in several of those pathways and are also in active cell cycle to a much higher extent. This means that there will be one radiation dose that kills most cancer cells (at least those in active cell cycle), and another higher dose that would start killing normal cells. In radiotherapy, we give a total dose that is quite high, but this total dose is fractioned into several of the lower doses so that as few normal cells as possible are killed. For instance, a curative dose for prostate cancer is 78 Gy (very high for human tissues), but this is broken down into 2 Gy doses given daily under 39 days.
What causes Cancer? Carcinogens or free radicals?
They both are somehow responsible for causing cancer. They both effects the body when we are exposed to these elements for a longer duration, giving them sufficient time to damage our cells and tissues which later becomes really fatal and causes cancer.A carcinogen is something that can cause you to have cancer. It may be a substance in the air, a product you use, or a chemical in foods and drinks. Their amount is what effects, the more you are exposed to these carcenogens, the higher are its chances to develop cancer. Examples can be, UV rays, chemicals present in tobacco and alcohol.Free radicles are highly reactive chemicals that have the potential to harm cells. They are the atoms with lone pair of oxygen. At high concentrations, however, free radicals can be hazardous to the body and damage all major components of cells, including DNA, proteins, and cell membranes. The damage to cells caused by free radicals, especially the damage to DNA, may play a role in the development of cancer and other health conditions. Moreover, some environmental toxins, such as cigarette smoke, some metals, and high-oxygen atmospheres, may contain large amounts of free radicals or stimulate the body’s cells to produce more free radicals.