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Kataegis
In molecular biology, kataegis describes a pattern of localized hypermutations identified in some Cancer Genome Project, cancer genomes, in which a large number of highly patterned Mutation, basepair mutations occur in a small region of DNA. The mutational clusters are usually several hundred basepairs long, alternating between a long range of C→T substitutional pattern and a long range of G→A substitutional pattern. This suggests that kataegis is carried out on only one of the two template strands of DNA during replication. Compared to other cancer-related mutations, such as chromothripsis, kataegis is more commonly seen; it is not an accumulative process but likely happens during one cycle of DNA replication, replication. The term ''kataegis (καταιγίς)'' is derived from the ancient Greek word for "thunderstorm". It was first used by scientists at the Wellcome Trust Sanger Institute to describe their observations of breast cancer cells. In the process of mapping mutatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromothripsis
Chromothripsis is a mutational process by which up to thousands of clustered chromosomal rearrangements occur in a single event in localised and confined genomic regions in one or a few chromosomes, and is known to be involved in both cancer and congenital diseases. It occurs through one massive genomic rearrangement during a single catastrophic event in the cell's history. It is believed that for the cell to be able to withstand such a destructive event, the occurrence of such an event must be the upper limit of what a cell can tolerate and survive. The chromothripsis phenomenon opposes the conventional theory that cancer is the gradual acquisition of genomic rearrangements and somatic mutations over time. The simplest model as to how these rearrangements occur is through the simultaneous fragmentation of distinct chromosomal regions (breakpoints show a non-random distribution) and then subsequent imperfect reassembly by DNA repair pathways or aberrant DNA replication mechanisms. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thymine
Thymine () (symbol T or Thy) is one of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T. The others are adenine, guanine, and cytosine. Thymine is also known as 5-methyluracil, a pyrimidine nucleobase. In RNA, thymine is replaced by the nucleobase uracil. Thymine was first isolated in 1893 by Albrecht Kossel and Albert Neumann from calf thymus glands, hence its name. Derivation As its alternate name (5-methyluracil) suggests, thymine may be derived by methylation of uracil at the 5th carbon. In RNA, thymine is replaced with uracil in most cases. In DNA, thymine (T) binds to adenine (A) via two hydrogen bonds, thereby stabilizing the nucleic acid structures. Thymine combined with deoxyribose creates the nucleoside deoxythymidine, which is synonymous with the term thymidine. Thymidine can be phosphorylated with up to three phosphoric acid groups, producing dTMP (deoxythymidine monophosphate), dTDP, or dTTP (for the di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromoplexy
Chromoplexy refers to a class of complex DNA rearrangement observed in the genomes of cancer cells. This phenomenon was first identified in prostate cancer by whole genome sequencing of prostate tumors. Chromoplexy causes genetic material from one or more chromosomes to become scrambled as multiple strands of DNA are broken and ligated to each other in a new configuration. In prostate cancer, chromoplexy may cause multiple oncogenic events within a single cell cycle, providing a proliferative advantage to a (pre-)cancerous cell. Several oncogenic mutations in prostate cancer occur through chromoplexy, such as disruption of the tumor suppressor gene '' PTEN'' or creation of the ''TMPRSS2-ERG'' fusion gene. Chromplexy was originally inferred by statistically analyzing the location of DNA breaks across the genome. Its prevalence across cancers is not known, because only a few types of tumors have been analyzed for chromoplexy in the published literature. However, it was detected in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glycosylase
Glycosylases ( EC 3.2) are enzymes that hydrolyze glycosyl compounds. They are a type of hydrolase (EC 3). In turn, glycosylases are divided into two groups: glycosidases—enzymes that hydrolyze O- and S-glycosyl compounds (EC 3.2.1) -- and enzymes that hydrolyze N-glycosyl compounds (EC 3.2.2). References {{Portal bar, Biology, border=no EC 3.2 Enzymes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
A Structure For Deoxyribose Nucleic Acid
"Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid" was the first article published to describe the discovery of the double helix structure of DNA, using X-ray diffraction and the mathematics of a helix transform. It was published by Francis Crick and James D. Watson in the scientific journal ''Nature'' on pages 737–738 of its 171st volume (dated 25 April 1953). This article is often termed a "pearl" of science because it is brief and contains the answer to a fundamental mystery about living organisms. This mystery was the question of how it is possible that genetic instructions are held inside organisms and how they are passed from generation to generation. The article presents a simple and elegant solution, which surprised many biologists at the time who believed that DNA transmission was going to be more difficult to deduce and understand. The discovery had a major impact on biology, particularly in the field of genetics, enabling later resear ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AP Site
In biochemistry and molecular genetics, an AP site (apurinic/apyrimidinic site), also known as an abasic site, is a location in DNA (also in RNA but much less likely) that has neither a purine nor a pyrimidine base, either spontaneously or due to DNA damage. It has been estimated that under physiological conditions 10,000 apurinic sites and 500 apyrimidinic may be generated in a cell daily. AP sites can be formed by spontaneous depurination, but also occur as intermediates in base excision repair.Abasic sites in DNA: repair and biological consequences in Saccharomyces cerevisiae. DNA Repair (Amst). 2004 Jan 5;3(1):1-12. In this process, a DNA glycosylase recognizes a damaged base and cleaves the N-glycosidic bond to release the base, leaving an AP site. A variety of glycosylases that recognize different types of damage exist, including oxidized or methylated bases, or uracil in DNA. The AP site can then be cleaved by an AP endonuclease, leaving 3'-hydroxyl and deoxyribose-5-ph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Error-prone TLS DNA Polymerase
Cognitive dimensions or cognitive dimensions of notations are design principles for notations, user interfaces and programming languages, described by researcher Thomas R.G. Green and further researched with Marian Petre. The dimensions can be used to evaluate the usability of an existing ''information artifact'', or as heuristics to guide the design of a new one, and are useful in Human-Computer Interaction design. Cognitive dimensions are designed to provide a lightweight approach to analyse the quality of a design, rather than an in-depth, detailed description. They provide a common vocabulary for discussing many factors in notation, UI or programming language design. Also, cognitive dimensions help in exploring the space of possible designs through ''design maneuvers'', changes intended to improve the design along one dimension. List of the cognitive dimensions Thomas Green originally defined 14 cognitive dimensions: ; Abstraction gradient : What are the minimum and ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lymphoma
Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enlarged lymph nodes, fever, drenching sweats, unintended weight loss, itching, and constantly feeling tired. The enlarged lymph nodes are usually painless. The sweats are most common at night. Many subtypes of lymphomas are known. The two main categories of lymphomas are the non-Hodgkin lymphoma (NHL) (90% of cases) and Hodgkin lymphoma (HL) (10%). The World Health Organization (WHO) includes two other categories as types of lymphoma – multiple myeloma and immunoproliferative diseases. Lymphomas and leukemias are a part of the broader group of tumors of the hematopoietic and lymphoid tissues. Risk factors for Hodgkin lymphoma include infection with Epstein–Barr virus and a history of the disease in the family. Risk factors f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Processivity
In molecular biology and biochemistry, processivity is an enzyme's ability to catalyze "consecutive reactions without releasing its substrate". For example, processivity is the average number of nucleotides added by a polymerase enzyme, such as DNA polymerase, per association event with the template strand. Because the binding of the polymerase to the template is the rate-limiting step in DNA synthesis, the overall rate of DNA replication during S phase of the cell cycle is dependent on the processivity of the DNA polymerases performing the replication. DNA clamp proteins are integral components of the DNA replication machinery and serve to increase the processivity of their associated polymerases. Some polymerases add over 50,000 nucleotides to a growing DNA strand before dissociating from the template strand, giving a replication rate of up to 1,000 nucleotides per second. DNA binding interactions Polymerases interact with the phosphate backbone and the minor groove of the DN ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dinucleotide
Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules within all life-forms on Earth. Nucleotides are obtained in the diet and are also synthesized from common nutrients by the liver. Nucleotides are composed of three subunit molecules: a nucleobase, a five-carbon sugar (ribose or deoxyribose), and a phosphate group consisting of one to three phosphates. The four nucleobases in DNA are guanine, adenine, cytosine and thymine; in RNA, uracil is used in place of thymine. Nucleotides also play a central role in metabolism at a fundamental, cellular level. They provide chemical energy—in the form of the nucleoside triphosphates, adenosine triphosphate (ATP), guanosine triphosphate (GTP), cytidine triphosphate (CTP) and uridine triphosphate (UTP)—throughout the cell for the many cellular functio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
