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Isoschizomer
Isoschizomers are pairs of restriction enzymes specific to the same recognition sequence. For example, SphI (CGTAC/G) and BbuI (CGTAC/G) are isoschizomers of each other. The first enzyme discovered which recognizes a given sequence is known as the prototype; all subsequently identified enzymes that recognize that sequence are isoschizomers. Isoschizomers are isolated from different strains of bacteria and therefore may require different reaction conditions. In some cases, only one out of a pair of isoschizomers can recognize both the methylated as well as unmethylated forms of restriction sites. In contrast, the other restriction enzyme can recognize only the unmethylated form of the restriction site. This property of some isoschizomers allows identification of methylation state of the restriction site while isolating it from a bacterial strain. For example, the restriction enzymes HpaII and MspI are isoschizomers, as they both recognize the sequence 5'-CCGG-3' when it is unme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Restriction Enzyme
A restriction enzyme, restriction endonuclease, REase, ENase or'' restrictase '' is an enzyme that cleaves DNA into fragments at or near specific recognition sites within molecules known as restriction sites. Restriction enzymes are one class of the broader endonuclease group of enzymes. Restriction enzymes are commonly classified into five types, which differ in their structure and whether they cut their DNA substrate at their recognition site, or if the recognition and cleavage sites are separate from one another. To cut DNA, all restriction enzymes make two incisions, once through each sugar-phosphate backbone (i.e. each strand) of the DNA double helix. These enzymes are found in bacteria and archaea and provide a defense mechanism against invading viruses. Inside a prokaryote, the restriction enzymes selectively cut up ''foreign'' DNA in a process called ''restriction digestion''; meanwhile, host DNA is protected by a modification enzyme (a methyltransferase) that modifi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neoschizomer
Neoschizomers are restriction enzymes that recognize the same nucleotide sequence as their prototype but cleave at a different site. In some special applications this is a very helpful feature. For example:Prototype MaeII A^CGT produces DNA fragments with a 2-base 5' extension Neoschizomer TaiI ACGT^ produces DNA fragments with a 4-base 3' extension Prototype ApaI GGGCC^C produces DNA fragments with a 4-base 3' extension Neoschizomer Bsp120I G^GGCCC produces DNA fragments with a 4-base 5' extension There are also other pairs of neoschizomers. Neoschizomers are a subset of isoschizomers. References * Rebase restriction enzyme database, http://rebase.neb.com/rebase/ See also Restriction enzymes {{enzyme-stub pl:Izoschizomery ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HpaII
HpaII (IntEnz: EC 3.1.21.4') is a restriction enzyme obtained from the microorganism ''Haemophilus parainfluenzae''. It is a DNA restriction enzyme, therefore it has the ability to cut the DNA from certain region as demonstrated below. It has the ability to produce cohesive ends, which are rather useful in constructing plasmids. HpaII will not cut sites that have been methylated by SssI methyltransferase or HpaII methyltransferase. When the sites have been methylated by MspI methyltransferase, the enzyme will cut 300 times slower than unmethylated DNA and 50 times slower if the DNA is hemi-methylated. McClelland, M., Nelson, M., Raschke, E. (1994). Nucleic Acids Research 22, No. 17, 3640-3659. This feature is exploited for determination of the clonal origin of a mammalian Mammals () are a group of vertebrate animals constituting the class (biology), class Mammalia (), characterized by the presence of mammary glands which in Female#Mammalian female, females produc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Biology
Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and physical structure of biological macromolecules is known as molecular biology. Molecular biology was first described as an approach focused on the underpinnings of biological phenomena - uncovering the structures of biological molecules as well as their interactions, and how these interactions explain observations of classical biology. In 1945 the term molecular biology was used by physicist William Astbury. In 1953 Francis Crick, James Watson, Rosalind Franklin, and colleagues, working at Medical Research Council unit, Cavendish laboratory, Cambridge (now the MRC Laboratory of Molecular Biology), made a double helix model of DNA which changed the entire research scenario. They proposed the DNA structure based on previous research done by Ro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isocaudomer
Isocaudomers are pairs of restriction enzymes that have slightly different recognition sequences, but upon cleavage of DNA, generate identical overhanging termini sequences. These sequences can be ligated to one another, but then form an asymmetrical sequence that cannot be cleaved by a restriction enzyme. Examples For example the enzymes Mbo I and BamH I are isocaudomers: Mbo I N*GATC N N CTAG*N BamH I G*GATC C C CTAG*G N represents any of the four nucleotides. Independently of which nucleotide is present when cleaving with MboI, after cleavage with either enzyme, all termini have the central tetranucleotide - GATC. This allows fragments generated with one enzyme to anneal with fragments generated with the other enzyme. This can be used for elimination of restriction site Restriction sites, or restriction recognition sites, are located on a DNA molecule containing specific (4-8 base pairs in length) sequences of nucleotides, which are recognized by restrict ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacterial Strain
In biology, a strain is a genetic variant, a subtype or a culture within a biological species. Strains are often seen as inherently artificial concepts, characterized by a specific intent for genetic isolation. This is most easily observed in microbiology where strains are derived from a single cell colony and are typically quarantined by the physical constraints of a Petri dish. Strains are also commonly referred to within virology, botany, and with rodents used in experimental studies. Microbiology and virology It has been said that "there is no universally accepted definition for the terms 'strain', 'variant', and 'isolate' in the virology community, and most virologists simply copy the usage of terms from others". A strain is a genetic variant or subtype of a microorganism (e.g., a virus, bacterium or fungus). For example, a "flu strain" is a certain biological form of the influenza or "flu" virus. These flu strains are characterized by their differing isoforms of surfac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Recognition Sequence
A recognition sequence is a DNA sequence to which a structural motif of a DNA-binding domain exhibits binding specificity. Recognition sequences are palindromes. The transcription factor Sp1 for example, binds the sequences 5'-(G/T)GGGCGG(G/A)(G/A)(C/T)-3', where (G/T) indicates that the domain will bind a guanine or thymine at this position. The restriction endonuclease PstI recognizes, binds, and cleaves the sequence 5'-CTGCAG-3'. A recognition sequence is different from a recognition site. A given recognition sequence can occur one or more times, or not at all, on a specific DNA fragment. A recognition site is specified by the position of the site. For example, there are two PstI recognition sites in the following DNA sequence fragment, starting at base 9 and 31 respectively. A recognition sequence is a specific sequence, usually very short (less than 10 bases). Depending on the degree of specificity of the protein, a DNA-binding protein can bind to more than one specific sequ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
