What are restriction enzymes and how are plasmids cut by restriction enzymes?
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Restriction enzymes (also called as restriction endonucleases) are the enzymes that cut DNA molecule at specific sites.
Different kinds of restriction enzymes are known that recognizes different DNA sequences. They recognizes palindromic sequences in DNA and cut within those specific palindromic sequences (also called as restriction sites). Length of sequences may vary but usually it is called as "4-base cutters" and "6-base cutters". Placement of cut also varies, some leaves "sticky ends" and some "blunt ends".
Palindromic sequences are the sequences in which one strand matches that of complementary strand when read from opposite direction.
Restriction enzymes found in bacteria and their role is to destroy DNA of invading viruses.
Plasmids used for recombinant DNA technology have recognition sequences for a number of restriction enzymes. This allows restriction enzyme to cut the plasmid at specific sequence. Ligation enzymes can then be used to ligate in new genomic sequences.
Restriction enzymes have two properties useful in recombinant DNA technology :
1) They cut DNA into fragments of a size suitable for cloning.
2) Many restriction enzymes make staggered cuts generating single-stranded sticky ends conducive to the formation of recombinant DNA.
Restriction enzymes cut a DNA molecule at a specific site. This enzyme scans a DNA molecule, looking for a particular sequence, usually of 4 to 6 nucleotides. Once it finds this recognition sequence, it stops and cuts the strands. This is known as enzyme digestion. On double stranded DNA the recognition sequence is on both strands, but runs in opposite directions. This allows the enzyme to cut both strands. Sometimes the cut is blunt, sometimes the cut is uneven with dangling nucleotides on one of the two strands. This uneven cut is known as sticky ends....
- 28 Sep 2020 @ 07:27