1 https socraticorg questionswhyarerestrictionenzymesimportantforrecombinantdnatechnology Restriction enzymes sometimes called molecular scissors PART 1 Background What do restriction enzymes do ID: 1009017
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1. Chapter 4: Restriction endonucleases1https://socratic.org/questions/why-are-restriction-enzymes-important-for-recombinant-dna-technologyRestriction enzymes sometimes called molecular scissors PART 1: BackgroundWhat do restriction enzymes do in nature?
2. Nuclease categoriesCleave the phosphodiester bonds between nucleotide subunits of nucleic acidsTwo typesEndonucleases – cut in internal position in a DNA strand Exonucleases – begin degradation from ends of DNA strands2
3. Restriction EndonucleasesBacteria and archaea have inhibiting or restricting “restriction modification systems” that protect against invading foreign DNA, primarily bacteriophages. Systems divided into classes I, II, IIIWe will focus on type II3
4. The bacterial restriction modification type II systemProtect bacteria against bacteriophages Certain bacteria strains were found to inhibit (restrict) the growth of bacteriophagesEffect was attributed to sequence-specific DNA restriction enzymesBacteria have restriction enzymes, also called restriction endonucleasescleave double stranded DNA at specific points into fragmentsThis prevents infection by bacteriophageBacteria protect their own DNA by methylating it so the restriction enzymes cannot recognize the site4/Wikipedia
5. Type II systems are characterized by 2 enzymesrestriction endonucleasecleaves foreign DNA methylase, methylates recognition sequences in own genome, preventing digestion by endonuclease 5
6. Compartmentalization of restriction and methylase enzymes in Gram negative bacteriaaid the distinction between foreign and bacterial DNA6