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Toxicology
Published in W. David Yates, Safety Professional’s Reference and Study Guide, 2020
Other classifications of chemicals or toxins include carcinogens, cocarcinogens, epigenetic, genotoxic, mutagen, clastogen, and teratogen, which are described in the following. Carcinogen: Any substance or agent known to cause cancer. Carcinogens do not adhere to the dose–response curve.Cocarcinogen: These agents, when applied immediately prior to or with a genotoxic carcinogen, enhance the oncogenic (cancerous) effect of the agent.Epigenetic: Changes in phenotype (appearance) or gene expression caused by mechanisms other than changes in the underlying DNA sequence.Genotoxic: These materials are known to be potentially mutagenic and carcinogenic in nature. They act directly by altering the DNA.Mutagen: A physical or chemical agent that changes the genetic material (usually DNA) of an organism and thus increases the frequency of mutagens above the natural background level.Teratogens: Any agent that can disturb the development of an embryo or fetus.
Genes and Genomics
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2020
It all started during the mid-twentieth century with scientists Conrad H. Waddington and Ernst Hadorn, who did extensive research focused on merging genetics and developmental biology, and has evolved into a new field, which we currently call epigenetics. The word epigenetics was coined by Waddington in 1942 and originally described the influence of genetic processes on development. During the 1990s, there was a renewed interest in genetic assimilation that led to the elucidation of the molecular basis of Waddington’s observations in which environmental stress caused genetic assimilation in fruit flies. Subsequently, research efforts focused on unraveling the epigenetic mechanisms related to these types of changes. Presently, DNA methylation is one of the most largely studied epigenetic modifications. The renewed interest in epigenetics has led to new findings about the relationship between epigenetic variations and many diseases such as cancers, immune disorders, mental retardation-associated disorders, and pediatric and psychiatric disorders.
Principles of Biology
Published in Arthur T. Johnson, Biology for Engineers, 2019
Epigenetic markers can incorporate environmental factors into genetic expression of the present generation so that various circumstances such as diet, stress, and prenatal nutrition affect genetic expression in future generations. Feeding B vitamins (methyl donors) to pregnant mice has been demonstrated to overcome genetic tendencies to diabetes and overweight in their offspring (Waterland and Jirtle, 2003). Fruit flies have shown epigenetic effects through at least 13 generations, and round worms through at least 40 generations (Jablonka and Raz, 2009). Even memory in mouse offspring can be improved via epigenetic properties of their parents’ genomes (Arai et al., 2009). Epigenetic DNA methylation may also contribute to long-term memory formation in humans (Biergans et al., 2016). Reversible epigenetic changes have been shown to be associated with behavior in honeybees. Young honeybees function as nurses to unemerged brood larva and nurse bees later become foragers. With methylation of a majority of genes these foragers have been made to revert to nurse behavior (Herb et al., 2012).
Epigenotoxicity: a danger to the future life
Published in Journal of Environmental Science and Health, Part A, 2023
Farzaneh Kefayati, Atoosa Karimi Babaahmadi, Taraneh Mousavi, Mahshid Hodjat, Mohammad Abdollahi
Epigenetic mechanisms are divided into DNA modifications, chromatin modifications, non-coding RNAs and RNA modifications, which produce a set of potential hereditary changes in gene expression;[2] thus, epigenetic markers can persevere throughout growth and likely pass from offspring to offspring. For example, the open state of chromatin is caused by chemical changes in histone proteins that facilitate gene expression by interacting with transcription factors and enzymes with DNA, or the closed state of heterochromatin, which prevents the initiation of transcription and suppresses gene expression. Although epigenetic markers are stable and regulate gene expression, environmental factors can act as stimuli; thus, altered epigenetic patterns may change phenotypic responses via different pathways and disruption of epigenetic modifiers.[3] These factors include air pollution, metals, pesticides, and electrical waste (E-waste), which have become more prevalent following urbanization and the expansion of industries. The role of environmental stimuli on epigenetic changes can be clearly understood in the case of identical twins. Although they have the same DNA sequence, epigenetic mechanisms such as DNA methylation and histone modification have led to phenotypic differences resulting from different exposure to environmental factors.[1]
Human health risk perspective study on characterization, quantification and spatial distribution of microplastics in surface water, groundwater and coastal sediments of thickly populated Chennai coast of South India
Published in Human and Ecological Risk Assessment: An International Journal, 2023
Srihari S., Subramani T., Prapanchan V. N., Peiyue Li
Recent studies have indicated that household wastewater contains a variety of fiber particles of polyester and polyamide, which would have been due to the utilization of groundwater contaminated with nylon fragments as a result of disintegration and percolation into the groundwater from these dumpsites. Nylon fragments are also found rampant in the beach sediments. These nylon fragments are resultant in the beach samples as a result of the degradation of fishing nets made up of polystyrene (PS) and polyamide (PA). These nylon fragments enter the marine environment due to the action of waves. The absorbed nylon micro-fragments due to wave action will find their route to the ultimate destination i.e., human beings via fishes that misinterpret it for food, ultimately rendering coastal fish consuming population vulnerable to the bisphenol A ill effect. It is known to cause a range of problems in human beings ranging from genetic expression changes (Galloway 2015) to multiple system disrupters in the human body, namely the endocrine, reproductive, and immune systems. The epigenetic changes can be inherited, reflecting changes in DNA modification’s methylation to histones and the expression of non-coding RNA (also micro-RNA). These also cause the disruption of the functions of thyroid stimulating hormones (TSH). Bisphenol A is also known to cause cardiovascular disease, type 2 diabetes, and abnormalities in the liver (Galloway 2015).
Posthumanism: Creation of ‘New Men’ Through Technological Innovation
Published in The New Bioethics, 2021
The expression and activity of genes depends not only the genetic code in the genome, but also on the microstructure (not the code) of the DNA itself and the proteins associated with its packaging in the chromosome; the chemical state of this microstructure and associated proteins constitutes the epigenome. Epigenetics is ‘the study of the mechanisms of temporal and spatial control of gene activity during the development of complex organisms’ (Holliday 1990, 329). Changes in the epigenome can be passed on the offspring via transgenerational epigenetic inheritance (Bernstein et al. 2007). Epigenetic changes wrought by one’s diet, behaviour, or surroundings can work their way into the germ line and echo far into the future (Morgan and Whitelaw 2008). Thus, changes in the phenotype include mechanisms that do not involve alterations of the DNA sequence; consequently, traits depend both on the genome and the epigenome, and modifications of the former alone may not result in the desired traits.