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Chain Termination Method
Sanger sequencing is a method of DNA sequencing that involves electrophoresis and is based on the random incorporation of chain-terminating dideoxynucleotides by DNA polymerase during in vitro DNA replication. After first being developed by Frederick Sanger and colleagues in 1977, it became the most widely used sequencing method for approximately 40 years. It was first commercialized by Applied Biosystems in 1986. More recently, higher volume Sanger sequencing has been replaced by next generation sequencing methods, especially for large-scale, automated genome analyses. However, the Sanger method remains in wide use for smaller-scale projects and for validation of deep sequencing results. It still has the advantage over short-read sequencing technologies (like Illumina) in that it can produce DNA sequence reads of > 500 nucleotides and maintains a very low error rate with accuracies around 99.99%. Sanger sequencing is still actively being used in efforts for public health initiat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dideoxynucleotide
Dideoxynucleotides are chain-elongating inhibitors of DNA polymerase, used in the Sanger method for DNA sequencing. They are also known as 2',3' because both the 2' and 3' positions on the ribose lack hydroxyl groups, and are abbreviated as ''ddNTPs'' (ddGTP, ddATP, ddTTP and ddCTP). Role in the Sanger method The Sanger method is used to amplify a target segment of DNA, so that the DNA sequence can be determined precisely. The incorporation of ddNTPs in the reaction valves are simply used to terminate the synthesis of a growing DNA strand, resulting in partially replicated DNA fragments. This is because DNA polymerase requires the 3' OH group of the growing chain and the 5' phosphate group of the incoming dNTP to create a phosphodiester bond. Sometimes the DNA polymerase will incorporate a ddNTP and the absence of the 3' OH group will interrupt the condensation reaction between the 5' phosphate (following the cleavage of pyrophospate) of the incoming nucleotide with the 3' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dideoxynucleotides
Dideoxynucleotides are chain-elongating inhibitors of DNA polymerase, used in the Sanger method for DNA sequencing. They are also known as 2',3' because both the 2' and 3' positions on the ribose lack hydroxyl groups, and are abbreviated as ''ddNTPs'' (ddGTP, ddATP, ddTTP and ddCTP). Role in the Sanger method The Sanger method is used to amplify a target segment of DNA, so that the DNA sequence can be determined precisely. The incorporation of ddNTPs in the reaction valves are simply used to terminate the synthesis of a growing DNA strand, resulting in partially replicated DNA fragments. This is because DNA polymerase requires the 3' OH group of the growing chain and the 5' phosphate group of the incoming dNTP to create a phosphodiester bond. Sometimes the DNA polymerase will incorporate a ddNTP and the absence of the 3' OH group will interrupt the condensation reaction between the 5' phosphate (following the cleavage of pyrophospate) of the incoming nucleotide with the 3' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DdNTP
Dideoxynucleotides are chain-elongating inhibitors of DNA polymerase, used in the Sanger method for DNA sequencing. They are also known as 2',3' because both the 2' and 3' positions on the ribose lack hydroxyl groups, and are abbreviated as ''ddNTPs'' (ddGTP, ddATP, ddTTP and ddCTP). Role in the Sanger method The Sanger method is used to amplify a target segment of DNA, so that the DNA sequence can be determined precisely. The incorporation of ddNTPs in the reaction valves are simply used to terminate the synthesis of a growing DNA strand, resulting in partially replicated DNA fragments. This is because DNA polymerase requires the 3' OH group of the growing chain and the 5' phosphate group of the incoming dNTP to create a phosphodiester bond. Sometimes the DNA polymerase will incorporate a ddNTP and the absence of the 3' OH group will interrupt the condensation reaction between the 5' phosphate (following the cleavage of pyrophospate) of the incoming nucleotide with the 3' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Sequencing
DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine. The advent of rapid DNA sequencing methods has greatly accelerated biological and medical research and discovery. Knowledge of DNA sequences has become indispensable for basic biological research, DNA Genographic Projects and in numerous applied fields such as medical diagnosis, biotechnology, forensic biology, virology and biological systematics. Comparing healthy and mutated DNA sequences can diagnose different diseases including various cancers, characterize antibody repertoire, and can be used to guide patient treatment. Having a quick way to sequence DNA allows for faster and more individualized medical care to be administered, and for more organisms to be identified and cataloged. The rapid speed of sequencing attained with modern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radioactive Fluorescent Seq
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are alpha decay ( ), beta decay ( ), and gamma decay ( ), all of which involve emitting one or more particles. The weak force is the mechanism that is responsible for beta decay, while the other two are governed by the electromagnetism and nuclear force. A fourth type of common decay is electron capture, in which an unstable nucleus captures an inner electron from one of the electron shells. The loss of that electron from the shell results in a cascade of electrons dropping down to that lower shell resulting in emission of discrete X-rays from the transitions. A common example is iodine-125 commonly used in medical settings. Radioactive decay is a stochastic (i.e. random) pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leroy Hood
Leroy "Lee" Edward Hood (born October 10, 1938) is an American biologist who has served on the faculties at the California Institute of Technology (Caltech) and the University of Washington. Hood has developed ground-breaking scientific instruments which made possible major advances in the biological sciences and the medical sciences. These include the first gas phase protein sequencer (1982), for determining the sequence of amino acids in a given protein; a DNA synthesizer (1983), to synthesize short sections of DNA; a peptide synthesizer (1984), to combine amino acids into longer peptides and short proteins; the first automated DNA sequencer (1986), to identify the order of nucleotides in DNA; ink-jet oligonucleotide technology for synthesizing DNA and nanostring technology for analyzing single molecules of DNA and RNA. The protein sequencer, DNA synthesizer, peptide synthesizer, and DNA sequencer were commercialized through Applied Biosystems, Inc. and the ink-jet tec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radioisotopic Labelling
Isotopic labeling (or isotopic labelling) is a technique used to track the passage of an isotope (an atom with a detectable variation in neutron count) through a reaction, metabolic pathway, or cell. The reactant is 'labeled' by replacing specific atoms by their isotope. The reactant is then allowed to undergo the reaction. The position of the isotopes in the products is measured to determine the sequence the isotopic atom followed in the reaction or the cell's metabolic pathway. The nuclides used in isotopic labeling may be stable nuclides or radionuclides. In the latter case, the labeling is called radiolabeling. In isotopic labeling, there are multiple ways to detect the presence of labeling isotopes; through their mass, vibrational mode, or radioactive decay. Mass spectrometry detects the difference in an isotope's mass, while infrared spectroscopy detects the difference in the isotope's vibrational modes. Nuclear magnetic resonance detects atoms with different gyroma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sequencing
In genetics and biochemistry, sequencing means to determine the primary structure (sometimes incorrectly called the primary sequence) of an unbranched biopolymer. Sequencing results in a symbolic linear depiction known as a sequence which succinctly summarizes much of the atomic-level structure of the sequenced molecule. DNA sequencing DNA sequencing is the process of determining the nucleotide order of a given DNA fragment. So far, most DNA sequencing has been performed using the chain termination method developed by Frederick Sanger. This technique uses sequence-specific termination of a DNA synthesis reaction using modified nucleotide substrates. However, new sequencing technologies such as pyrosequencing are gaining an increasing share of the sequencing market. More genome data are now being produced by pyrosequencing than Sanger DNA sequencing. Pyrosequencing has enabled rapid genome sequencing. Bacterial genomes can be sequenced in a single run with several times co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiography
Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeutic") and industrial radiography. Similar techniques are used in airport security (where "body scanners" generally use backscatter X-ray). To create an image in conventional radiography, a beam of X-rays is produced by an X-ray generator and is projected toward the object. A certain amount of the X-rays or other radiation is absorbed by the object, dependent on the object's density and structural composition. The X-rays that pass through the object are captured behind the object by a detector (either photographic film or a digital detector). The generation of flat two dimensional images by this technique is called projectional radiography. In computed tomography (CT scanning) an X-ray source and its associated detectors rotate around t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autoradiography
An autoradiograph is an image on an X-ray film or nuclear emulsion produced by the pattern of decay emissions (e.g., beta particles or gamma rays) from a distribution of a radioactive substance. Alternatively, the autoradiograph is also available as a digital image (digital autoradiography), due to the recent development of scintillation gas detectors or rare earth phosphorimaging systems. The film or emulsion is apposed to the labeled tissue section to obtain the autoradiograph (also called an autoradiogram). The ''auto-'' prefix indicates that the radioactive substance is within the sample, as distinguished from the case of historadiography or microradiography, in which the sample is marked using an external source. Some autoradiographs can be examined microscopically for localization of silver grains (such as on the interiors or exteriors of cells or organelles) in which the process is termed micro-autoradiography. For example, micro-autoradiography was used to examine whethe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
