How to find the length of the recognition site of the endonuclease

Restriction endonucleases, restriction enzymes (from Latin restrictio - restriction) are a group of enzymes belonging to the class of hydrolases that catalyze the hydrolysis reaction of nucleic acids. Unlike exonucleases, restriction enzymes cleave nucleic acids not from the end of the molecule, but in the middle. At the same time, each restriction enzyme recognizes a certain DNA section with a length of four base pairs and cleaves the nucleotide chain inside or outside the recognition site. Protection of the bacterial genome from its own restriction enzyme is carried out by methylation of the nucleotide residues of adenine and cytosine (masking). When restriction is carried out under suboptimal conditions, endonucleases exhibit stellar activity (a decrease in restriction specificity). There are three main types (or classes) of restriction enzymes, the recognition sites for which can be symmetrical (palindromic) and asymmetric: Restriction enzymes of the first type (for example, EcoK from Escherichia coli K12) recognize a certain nucleotide sequence and cut a double-stranded DNA molecule near this sequence at an arbitrary point, and the place of the cut itself is not strictly specific (apparently, after the formation of a complex with DNA, the enzyme interacts nonspecifically with the remote region of DNA or moves along the DNA strand). Restriction enzymes of the second type (for example, EcoRI, XbaI) recognize a certain sequence and cut the DNA double helix at a certain fixed point within this sequence. Restriction enzymes of this type recognize palindromic sequences that have a central axis and are read equally on both sides of the axis of symmetry. Restriction enzymes of the third intermediate type (for example, EcoPI) recognize the desired sequence and cut the double-stranded DNA molecule, retreating a certain number of nucleotide pairs from its end (or at several points at different distances from the recognition site). In this case, DNA fragments are formed either with smooth (blunt) ends or with protruding (sticky) 5'- or 3'-ends. These restriction enzymes recognize asymmetric sites. These properties are widely used in various in vitro DNA assembly methods, such as Golden Gate assembly. By 2007, more than three thousand restriction endonucleases had been isolated. More than six hundred restrictases are available commercially and are routinely used in laboratories for DNA modification and genetic engineering. #palindrome #Genetics #DNA #restrictionEnzyme #recognitionSite #recognitionSequence #NikolaysGeneticsLessons #palindromicSequence #protein #endonuclease #gelElectrophoresis #agarose #usingAGelElectrophoresisMachine #DNAFingerprinting #howDoesAGelElectrophoresisMachineWork #biology #science #negativelyChargedDNA #restrictionEnzymes #guppies #basePairs #DNAFragments #DNALadder #biotechnology #HighSchool #stepsInElectrophoresis