restriction enzymes

Palindromic Sequences

Restriction enzymes cut double-stranded DNA* at specific locations based the pattern of bases found at those locations. These enzymes predictably cut both strands because the sequences they recognize are palindromic. That is the recognition sequences are short string of identical bases on both DNA strands.

Palindromic sequences are similar to language palindromes, but follow a distinct set of rules. Any string of bases can be made into a palindromic sequence by following these rules.

Restriction Enzymes

Restriction enzymes cut DNA* at specific sites based on the sequence of bases along the strand at the cut site. These enzymes were first identified and studied in strains of the bacteria E. Coli in the 1950’s and 60’s. The term restriction was used to describe them because their activity restricted the growth of viruses that infect E. coli.

Restriction enzymes are nucleases - enzymes that cut nucleic acid polymers (i.e. DNA and RNA). There are two types of nuclease: endonuclease and exonuclease. Endonucleases make cuts within a DNA polymer. Exonucleases remove individual nucleotides* from the end of a strand. Restriction enzymes are a type of endonuclease - they cut at specific sites in the middle of DNA strands.

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