The General Properties Of Restriction Enzymes Essay

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Q3/ Outline the following topics: (a) The general properties of Restriction enzymes and their use in recombinant DNA. Restriction enzymes are also known as restriction endonucleases, which recognise and cut a specific sequence of double-stranded DNA at that recognition sites. These enzymes protect the bacteria from foreign DNA (e.g. bacteriophages; Lamda phage), by digesting them into smaller pieces. The restrictive host protects its own DNA by a modification involving methylation of certain bases within DNA which constitute the recognition sequences for the restriction endonuclease. Restriction Enzymes search for exact sequences of defined length, like 4 bp long (e.g., GTAC), some 6 (e.g., GAATTC), and still others 8 or more and their recognition sites are palindromes, or sequence which reads the same on both strands in the 5 ' --> 3 ' direction. Example, the site of recognition for HindIII is 5 'AAGCTT3 '. The arrows are the points at which the enzyme causes breaks in the DNA backbone and separating them by weakening the hydrogen bonds. This type of cut is staggered, which generates sticky ends because they are able to bind to a complementary single-stranded region. Restriction Enzymes can also produce fragments without single-stranded ends called a blunt cut, example by Eco RV, as shown below. Any DNA molecule, from viral to human, contains restriction-enzyme target sites purely by chance and therefore may be cut into defined fragments of a size suitable for
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