|
5-Methylcytosine
5-Methylcytosine (5mC) is a methylation, methylated form of the DNA base cytosine (C) that regulates gene Transcription (genetics), transcription and takes several other biological roles. When cytosine is methylated, the DNA maintains the same sequence, but the Gene expression#DNA methylation and demethylation in transcriptional regulation, expression of methylated genes can be altered (the study of this is part of the field of epigenetics). 5-Methylcytosine is incorporated in the nucleoside 5-Methylcytidine, 5-methylcytidine. Discovery While trying to isolate the bacterial toxin responsible for tuberculosis, W.G. Ruppel isolated a novel nucleic acid named tuberculinic acid in 1898 from ''Mycobacterium tuberculosis, Tubercle bacillus''. The nucleic acid was found to be unusual, in that it contained in addition to thymine, guanine and cytosine, a methylated nucleotide. In 1925, Treat Baldwin Johnson, Johnson and Coghill successfully detected a minor amount of a methylated cytosi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epigenetics
In biology, epigenetics is the study of changes in gene expression that happen without changes to the DNA sequence. The Greek prefix ''epi-'' (ἐπι- "over, outside of, around") in ''epigenetics'' implies features that are "on top of" or "in addition to" the traditional (DNA sequence based) genetic mechanism of inheritance. Epigenetics usually involves a change that is not erased by cell division, and affects the regulation of gene expression. Such effects on cellular and physiological traits may result from environmental factors, or be part of normal development. The term also refers to the mechanism of changes: functionally relevant alterations to the genome that do not involve mutation of the nucleotide sequence. Examples of mechanisms that produce such changes are DNA methylation and histone modification, each of which alters how genes are expressed without altering the underlying DNA sequence. Further, non-coding RNA sequences have been shown to play a key role in the r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
5-hydroxymethylcytosine
5-Hydroxymethylcytosine (5hmC) is a DNA pyrimidine nitrogen base derived from cytosine. It is potentially important in epigenetics, because the hydroxymethyl group on the cytosine can possibly switch a gene on and off. It was first seen in bacteriophages in 1952. However, in 2009 it was found to be abundant in human and mouse brains, as well as in embryonic stem cells. In mammals, it can be generated by oxidation of 5-methylcytosine, a reaction mediated by TET enzymes. Localization Every mammalian cell seems to contain 5-Hydroxymethylcytosine, but the levels vary significantly depending on the cell type. The highest levels are found in neuronal cells of the central nervous system. The amount of hydroxymethylcytosine increases with age, as shown in mouse hippocampus and cerebellum. Function The exact function of this nitrogen base is still not fully elucidated, but it is thought that it may regulate gene expression or prompt DNA demethylation. This hypothesis is supported by th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CpG Site
The CpG sites or CG sites are regions of DNA where a cytosine nucleotide is followed by a guanine nucleotide in the linear sequence of bases along its 5' → 3' direction. CpG sites occur with high frequency in genomic regions called CpG islands. Cytosines in CpG dinucleotides can be methylated to form 5-methylcytosines. Enzymes that add a methyl group are called DNA methyltransferases. In mammals, 70% to 80% of CpG cytosines are methylated. Methylating the cytosine within a gene can change its expression, a mechanism that is part of a larger field of science studying gene regulation that is called epigenetics. Methylated cytosines often mutate to thymines. In humans, about 70% of promoters located near the transcription start site of a gene (proximal promoters) contain a CpG island. CpG characteristics Definition ''CpG'' is shorthand for ''5'—C—phosphate—G—3' '', that is, cytosine and guanine separated by only one phosphate group; phosphate links any two ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transcription (genetics)
Transcription is the process of copying a segment of DNA into RNA for the purpose of gene expression. Some segments of DNA are transcribed into RNA molecules that can encode proteins, called messenger RNA (mRNA). Other segments of DNA are transcribed into RNA molecules called non-coding RNAs (ncRNAs). Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript. In virology, the term transcription is used when referring to mRNA synthesis from a viral RNA molecule. The genome of many RNA viruses is composed of negative-sense RNA which acts as a template for positive sense viral messenger RNA - a necessary step in the synthesis of viral proteins needed for viral replication. This process is catalyzed by a viral RNA dependent RNA polymerase. Background A DNA transcription unit encoding ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methylation
Methylation, in the chemistry, chemical sciences, is the addition of a methyl group on a substrate (chemistry), substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen#Compounds, hydrogen atom. These terms are commonly used in chemistry, biochemistry, soil science, and biology. In biological systems, methylation is Catalysis, catalyzed by enzymes; such methylation can be involved in modification of heavy metals, regulation of gene expression, regulation of Protein#Functions, protein function, and RNA processing. ''In vitro'' methylation of tissue samples is also a way to reduce some histology#Histological Artifacts, histological staining artifacts. The reverse of methylation is demethylation. In biology In biological systems, methylation is accomplished by enzymes. Methylation can modify heavy metals and can regulate gene expression, RNA processing, and protein function. It is a key pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytosine
Cytosine () (symbol C or Cyt) is one of the four nucleotide bases found in DNA and RNA, along with adenine, guanine, and thymine ( uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at position 2). The nucleoside of cytosine is cytidine. In Watson–Crick base pairing, it forms three hydrogen bonds with guanine. History Cytosine was discovered and named by Albrecht Kossel and Albert Neumann in 1894 when it was hydrolyzed from calf thymus tissues. A structure was proposed in 1903, and was synthesized (and thus confirmed) in the laboratory in the same year. In 1998, cytosine was used in an early demonstration of quantum information processing when Oxford University researchers implemented the Deutsch–Jozsa algorithm on a two qubit nuclear magnetic resonance quantum computer (NMRQC). In March 2015, NASA scientists reported the formation of cytosine, alon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deamination
Deamination is the removal of an amino group from a molecule. Enzymes that catalysis, catalyse this reaction are called deaminases. In the human body, deamination takes place primarily in the liver; however, it can also occur in the kidney. In situations of excess protein intake, deamination is used to break down amino acids for energy. The amino group is removed from the amino acid and converted to ammonia. The rest of the amino acid is made up of mostly carbon and hydrogen, and is recycled or oxidized for energy. Ammonia is toxic to the human system, and enzymes convert it to urea or uric acid by addition of carbon dioxide molecules (which is not considered a deamination process) in the urea cycle, which also takes place in the liver. Urea and uric acid can safely diffuse into the blood and then be excreted in urine. Deamination reactions in DNA Cytosine Spontaneous deamination is the hydrolysis reaction of cytosine into uracil, releasing ammonia in the process. This can occu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tuberculinic Acid
Tuberculinic acid is a noncanonical nucleic acid initially identified as the poison of ''Tubercle bacillus'' (=''Mycobacterium tuberculosis''), the principal causative bacterium of tuberculosis. Its discovery was one of the most important landmarks in understanding tuberculosis and in molecular biology. It is regarded as the most toxic component of the bacillus. It was from this compound that DNA methylation was discovered as it was the first molecule found to contain 5-methylcytosine. In addition it contains thymine, guanine and cytosine. Discovery It was first identified by a German people, German chemist W.G. Ruppel in 1898 while trying to isolate the bacterial toxin responsible for tuberculosis. From the crushed bacilli, specifically the protein tuberculin, he isolated two toxic substances, namely a base (chemistry), basic compound which he called tuberculosamine, and a nucleotide he named tuberculisäure, later to be anglicization, anglicised to tuberculinic acid. He claimed th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
5-Methylcytidine
5-Methylcytidine is a modified nucleoside derived from 5-methylcytosine. It is found in ribonucleic acid Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins ( messenger RNA). RNA and deoxyr ...s of animal, plant, and bacterial origin. References Nucleosides Pyrimidones Hydroxymethyl compounds {{Carbohydrate-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Treat Baldwin Johnson
Treat Baldwin Johnson (29 March 1875 – 28 July 1947) was an American organic chemist and Sterling Professor at Yale University from 1928–1943. Early life and education Treat Baldwin Johnson was born in Bethany, Connecticut, on 29 March 1875, the oldest of three sons of Dwight Lauren Johnson and Harriet Adeline Baldwin. He was educated at Ansonia high school and graduated from the Sheffield Scientific School of Yale University in 1898, where he obtained work as a laboratory assistant and began a Ph.D. degree under the supervision of H L Wheeler. By the time of its completion in 1901, Johnson had published seven scientific papers relating mainly to imidoesters. Career Johnson became an instructor of chemistry at the Sheffield Scientific School in 1902 and then an assistant professor in 1909. He specialized in organic chemistry and was promoted to full professor in 1914. In 1918, he received the Nichols Medal of the American Chemical Society in recognition of his work on pyr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Expression
Gene expression is the process (including its Regulation of gene expression, regulation) by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, proteins or non-coding RNA, and ultimately affect a phenotype. These products are often proteins, but in non-protein-coding genes such as Transfer RNA, transfer RNA (tRNA) and Small nuclear RNA, small nuclear RNA (snRNA), the product is a functional List of RNAs, non-coding RNA. The process of gene expression is used by all known life—eukaryotes (including multicellular organisms), prokaryotes (bacteria and archaea), and viruses—to generate the macromolecule, macromolecular machinery for life. In genetics, gene expression is the most fundamental level at which the genotype gives rise to the phenotype, ''i.e.'' observable trait. The genetic information stored in DNA represents the genotype, whereas the phenotype results from the "interpretation" of that informati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
APOBEC
image:Apobec.J.Steinfeld.D.png, 300px, upExample of a member of the APOBEC family, APOBEC-2. A cytidine deaminase from ''Homo sapiens''.; ; rendered usinPyMOL APOBEC ("apolipoprotein B mRNA editing enzyme, catalytic polypeptide") is a family of evolutionarily conserved cytidine deaminases. Function A mechanism of generating protein diversity is mRNA editing. The APOBEC family of proteins perform mRNA modifications by deaminating cytidine bases to uracil. The N-terminal domain of APOBEC-like proteins is the catalytic domain, while the C-terminal domain is a pseudocatalytic domain. More specifically, the catalytic domain is a zinc dependent cytidine deaminase domain and is essential for cytidine deamination. The positively charged zinc ion in the catalytic domain attracts to the partial-negative charge of RNA. In the case of APOBEC-1, the mRNA transcript of intestinal apolipoprotein B is altered. RNA editing by APOBEC-1 requires homodimerization and this complex interacts wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
