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您请求的操作仅限于组中的用户:==表观遗传学机制==[[文件:DNA甲基化。png|拇指|DNA甲基化]][[文件:DNA甲基化。jpeg|拇指|图4:组蛋白]][[文件:DNA甲基化。jpeg|拇指|图5:DNA被标记为类似化学基团的标志。表观遗传变化以不同的方式影响基因表达。表观遗传变化的类型包括:DNA甲基化:指的是体内一种化学反应，一种叫做甲基的小分子被添加到DNA、蛋白质或其他分子中。甲基的加入会影响一些分子在体内的行为。在DNA中，这个基团通常被添加到特定的位置，阻止附着在DNA上的蛋白质“读取”基因。当这个化学基团被移除时，这个过程叫做去甲基化。在大多数情况下，甲基化使基因“关闭”，而去甲基化使基因“打开”。组蛋白修饰:DNA包裹在组蛋白(一种蛋白质)上。如果组蛋白紧紧地包裹在DNA上，它们就不能被“读取”基因的蛋白质接触到。包裹在组蛋白周围的基因被“关闭”而没有包裹在组蛋白周围的基因则被“打开”。化学基团可以从组蛋白中添加或移除，并改变基因是打开(“打开”)还是包裹(“关闭”)。 * Non-coding RNA: DNA directs for making coding and non-coding RNA. Coding RNA is used to make proteins. Non-coding RNA helps control gene expression which it does attaching to coding RNA, along with certain proteins, to break down the coding RNA so that it cannot be used to make proteins. Non-coding RNA may also recruit proteins to modify histones to turn genes “on” or “off.”CDC Epigenetics Available:https://www.cdc.gov/genomics/disease/epigenetics.htm (accessed 26.7.2022) Epigenetics began over 60 years ago. During the 1970s it started becoming more prominent with the arrival of molecular biology and during the last 10–15 years, has emerged as a stand-alone discipline complementary to genetics. W.W. Weber, in Comprehensive Medicinal Chemistry II, 2007 Available:https://www.sciencedirect.com/referencework/9780080450445/comprehensive-medicinal-chemistry-ii (accessed 26.7.2022) Image 4: PDX1 is an essential transcription factor for proper development and function of pancreatic beta cells. Poor maternal nutrition is linked to intrauterine growth restriction (IUGR) and low birth weight, and can result in decreased expression of PDX1 through decreased histone acetylation at the PDX1 proximal promoter. Reduced expression of PDX1 may result in improper formation of beta cells and increase the risk of type-2 diabetes in the offspring Image 5: In every cell, DNA is tagged with chemical groups-like flags on the DNA-that make up the epigenetic code and act as guideposts. These flags help the cell's machinery know when to activate or inactivate a gene. In healthy cells, these flags are correctly placed and genes are expressed in the right proportions. However, in many tumor cells the flags are incorrectly applied. One form of incorrect DNA flagging occurs when extreme amounts of otherwise healthy methyl chemical groups, which act like on/off switches for a gene, are incorrectly added to many places on the cell's DNA. Instead of a cell chugging along with its natural, biological jobs, these newly added methyl groups cause the cell to act erratically, leading to the cell expressing genes at the wrong levels, or not at all. This generally disrupts the normal flow of information in the cell. Importantly, these flags can turn off key defensive genes that help protect the cell from becoming cancerous and disrupt other processes. When this occurs, it's called "CpG Island Methylation Phenotype," or CIMP for short. For a brief explanation watch this 5 minute video. {{#ev:youtube|v=_aAhcNjmvhc|300}} Carlos Guerrero-Bosagna. What is epigenetics. Available from: https://m.youtube.com/watch?v=_aAhcNjmvhc[last accessed 28/7/2022]

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