DNA modification in genetically aspect

Deoxyribonucleic acid (DNA) is a molecule that includes the genetic instructions worn in the development and functioning of all known living organisms and many viruses. DNA is a nucleic acid alongside proteins and carbohydrates, nucleic acids compose the three major molecular essential for the human being to survive in their lives. Most DNA molecules are double-stranded helices, consisting of two long biopolymers prepared of simpler units called nucleotides.

每个核苷酸是nucleobase(鸟嘌呤的准备,adenine, thymine, and cytosine), which uses the letters G, A, T, and C, as well as a backbone use in making of alternate sugars(deoxyribose) and phosphate groups (related to phosphoric acid), with the nucleobases (G, A, T, C) attached to the sugars.

随着两条链分离，生物信息被复制。DNA的很大一部分（人类的98％以上）是非编码的，这意味着这些部分不同意编码蛋白质的函数。

History of DNA

图：Geo logical tree of humanity

DNA was firstly unreachable by the Swiss physician Friedrich Miescher who, in 1869, who uncovered a microscopic substance in the pus of discarded surgical bandages. As it inhabited in the nuclei of cells, so he called it "nuclein" In 1878, Albrecht Kossel secluded the non-protein component of "nuclein", nucleic acid, and after that isolated its five primary nucleobases. In 1919, Phoebus Levene recognized the base, sugar and phosphate nucleotide unit.Levene recommended that DNA consisted of a string of nucleotide units linked together through the phosphate groups. However, Levene considered the chain was short and the bases repeated in a fixed order. In 1937 William Astbury shaped up the first X-ray diffraction patterns that showed that DNA had a regular structure.

DNA修饰

用于分子应用的DNA接地经常需要超出约束酶消化，碎片或PCR扩增的样品处理。修改酶可用于操纵或修复下游应用的DNA，例如：

• Recombinant DNA assembly for subsequent cloning
• PCR扩增
• DNA标记或探测
• Sequencing

Chemical modification of DNA or packaging

The expression of genes is prejudiced by how the DNA is packaged in chromosomes, in a structure called chromatin. Base modifications are to be occupied in packaging, with regions that have low or no gene expression frequently containing high levels of methylation of cytosine bases. DNA packaging and its influence on gene expression can also arise by covalent modifications of the histone protein core around which DNA is covered in the chromatin structure or else by remodeling carried out by chromatin remodeling complexes (see Chromatin remodeling). There is, further, crosstalk between DNA methylation and histone modification, so they can coordinately concern chromatin and gene expression.

Damage

DNA can be injured by many sorts of mutagens, which may make changes in the DNA sequence. Mutagens comprise oxidizing agents, alkylating agents and also high-energy electromagnetic radiation like ultraviolet light and X-rays. The type of DNA damage formed depends on the type of mutagen. For example, UV light causes in damage of DNA by producing thymine dimers, which are inter related between pyrimidine bases.

Focusing area of DNA Modification

DNA缺口正常，限制性核酸内切酶与它们在DNA中的识别序列结合，并同时水解双链体的两个链。两个独立的水解反应并行进展，最常见于每个酶内两个催化位点的存在，一种用于水解每条链。已经化了技术，以修改限制酶仅水解仅一根双链体的作用，以制造“划痕”而不是切割的DNA分子。

DNA END TREATING:Producing DNA samples by shearing, nebulization, restriction enzyme digestion or PCR amplification habitually leaves DNA molecules with ends irreconcilable for downstream experiments. Selective enzymatic treatment is worn to prepare DNA for ligation.

• DNA钝
• DNA磷酸化 /去磷酸化

DNA REPAIR:DNA容易受到许多来源的污垢，包括氧化，紫外线辐射，电离辐射，苯酚/氯仿提取，机械剪切，福尔马林固定（提取后）或长期存储。DNA翻新蛋白质和过程可以促进对环境样品的诊断分析。

DNA和蛋白甲基化：

甲基化对胞嘧啶碱基和组蛋白上的DNA进行化学修饰。操纵分子的形状方式，因此结合了分辨基因转录状态的各种调节蛋白。通常，甲基在情感上与与脊椎动物中转录基因抑制相关的鸟嘌呤（CpG二核苷酸）附近的胞嘧啶（5MC）（5MC）涉及。

DNA LIGATION:

DNA的连接是许多现代分子生物学工作流程中的中间步骤。DNA连接酶催化连接相邻DNA残基的3'羟基和5'磷酸的磷酸二酯键的构型。

生命的分泌

“Once you learn that, you’ll never stay the same again.”

“ When you raise up you, lean to get told that the world is the way it is and your life is just to live your life inside the world, try not to punch into the walls too much, try to get a nice family, b happy secure a little money. That’s a very petite life. Life can be much broader, once you determine one simple fact, and that is that everything which is surrounded you that you call life was made up by people that were no smarter than you. And you can revolutionize it, you can influence it, you can build your own things that other people can use. Once you learn that, you’ll never remain the same again.”