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The concept of restriction endonuclease, which is an enzyme that cleaves DNA into fragments at or near specific recognition sites within molecules known as restriction sites. The document also explains the process of restriction digestion and how host DNA is protected by a modification enzyme. The recognition sequences can also be classified by the number of bases in its recognition site, usually between 4 and 8 bases. The document also mentions the recognition site EcoRISmaI and blunt ends.
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A complex organic substance present in living cells, whose molecules consist of many nucleotides linked in a long chain. E.g.- DNA, RNA
Nuclease Nucleases cleave the phosphodiester bonds of nucleic acids and may be endo or exo, DNases or RNases, topoisomerases, recombinases, ribozymes, or RNA splicing enzymes. Endonuclease Enzymes that cleave the phosphodiester bond within a polynucleotide chain (namely DNA or RNA).
Restriction endonuclease/ restriction enzyme A restriction enzyme is an enzyme that cleaves DNA into fragments at or near specific recognition sites within molecules known as restriction sites
Type I enzymes (EC 3. 1. 21. 3 ) cleave at sites remote from a recognition site; require both ATP and S-adenosyl-L-methionine to function; multifunctional protein with both restriction digestion and methylase (EC 2. 1. 1. 72 ) activities. Type II enzymes (EC 3. 1. 21. 4 ) cleave within or at short specific distances from a recognition site; most require magnesium; single function (restriction digestion) enzymes independent of methylase. Type III enzymes (EC 3. 1. 21. 5 ) cleave at sites a short distance from a recognition site; require ATP (but do not hydrolyse it); S-adenosyl-L- methionine stimulates the reaction but is not required; exist as part of a complex with a modification methylase (EC 2. 1. 1. 72 ). Type IV enzymes target modified DNA, e.g. methylated, hydroxymethylated and glucosyl-hydroxymethylated DNA Type V enzymes utilize guide RNAs (gRNAs). Types of restriction enzymes