Difference Between Mutagen and Carcinogen | Definition, Causative Agents, Function, Effect
To adapt some biological terminology, a mutagen is classified based on its genotypic effects (does it cause mutations), while a carcinogen is. The somatic mutation theory of cancer holds that these agents cause cancer by inducing the mutation of somatic Relation between mutagens and carcinogens. In genetics, a mutagen is a physical or chemical agent that changes the genetic material, usually DNA, of an organism and thus increases the frequency of mutations above the natural background level. As many mutations can cause cancer, mutagens are therefore also likely to be carcinogens, The association of exposure to radiation and cancer had been observed as.
The most widely used test was developed in the s by Bruce Ames, who worked with Salmonella typhimurium. This Ames test uses two auxotrophic histidine mutations, which revert by different molecular mechanisms Figure Further properties were genetically engineered into these strains to make them suitable for mutagen detection.
First, they carry a mutation that inactivates the excision-repair system described later. Second, they carry a mutation that eliminates the protective lipopolysaccharide coating of wild-type Salmonella to facilitate the entry of many different chemicals into the cell.
Figure Ames test results showing the mutagenicity of aflatoxin B1, which is also a potent carcinogen. The TA strain is highly sensitive to reversion through base-pair more Bacteria are evolutionarily a long way removed from humans.
Can the results of a test on bacteria have any real significance in detecting chemicals that are dangerous for humans? First, we have seen that the genetic and chemical nature of DNA is identical in all organisms, so a compound acting as a mutagen in one organism is likely to have some mutagenic effects in other organisms. Second, Ames devised a way to simulate the human metabolism in the bacterial system.
In mammals, much of the important processing of ingested chemicals takes place in the liver, where externally derived compounds normally are detoxified or broken down. In some cases, the action of liver enzymes can create a toxic or mutagenic compound from a substance that was not originally dangerous Figure Ames incorporated mammalian liver enzymes in his bacterial test system, using rat livers for this purpose.
Difference Between Mutagen and Carcinogen
Figure outlines the procedure used in the Ames test. Figure The metabolic conversion of benzo a pyrene BP into a mutagen and a carcinogen. Benzo a pyrene goes through several steps a as it is made more water soluble prior to excretion. One of the intermediates in this process, a diol epoxide 3is capable more Figure Summary of the procedure used for the Ames test.
Mutagen - Wikipedia
First, rat liver enzymes are mobilized by injecting the animals with Arochlor. Enzymes from the liver are used because they carry out the metabolic processes of detoxifying and toxifying body chemicals. Chemicals detected by this test can be regarded not only as potential carcinogens sources of somatic mutationsbut also as possible causes of mutations in germinal cells. Because the test system is so simple and inexpensive, many laboratories throughout the world now routinely test large numbers of potentially hazardous compounds for mutagenicity and potential carcinogenicity.
More recent approaches with sensitive analytical methods have shown that there may be non-linear or bilinear dose-responses for genotoxic effects, and that the activation of DNA repair pathways can prevent the occurrence of mutation arising from a low dose of mutagen.
Some however may act on the replication mechanism and chromosomal partition. Many mutagens are not mutagenic by themselves, but can form mutagenic metabolites through cellular processes, for example through the activity of the cytochrome P system and other oxygenases such as cyclooxygenase. Ionizing radiations such as X-raysgamma rays and alpha particles cause DNA breakage and other damages. The most common lab sources include cobalt and cesium Radioactive decaysuch as 14C in DNA which decays into nitrogen.
DNA reactive chemicals[ edit ] A DNA adduct at center of the mutagenic metabolite of benzo[a]pyrene from tobacco smoke.
A large number of chemicals may interact directly with DNA. However, many such as PAHs, aromatic amines, benzene are not necessarily mutagenic by themselves, but through metabolic processes in cells they produce mutagenic compounds. Reactive oxygen species ROS — These may be superoxidehydroxyl radicals and hydrogen peroxideand large number of these highly reactive species are generated by normal cellular processes, for example as a by-products of mitochondrial electron transportor lipid peroxidation.
Deaminating agents, for example nitrous acid which can cause transition mutations by converting cytosine to uracil. Alkylating agents such as ethylnitrosourea. The compounds transfer methyl or ethyl group to bases or the backbone phosphate groups.
Guanine when alkylated may be mispaired with thymine. Some may cause DNA crosslinking and breakages.
Nitrosamines are an important group of mutagens found in tobacco, and may also be formed in smoked meats and fish via the interaction of amines in food with nitrites added as preservatives. Other alkylating agents include mustard gas and vinyl chloride. Aromatic amines and amides have been associated with carcinogenesis since when German physician Ludwig Rehn observed high incidence of bladder cancer among workers in German synthetic aromatic amine dye industry.
Alkaloid from plants, such as those from Vinca species,[ citation needed ] may be converted by metabolic processes into the active mutagen or carcinogen.