BIO130H1 Study Guide - Final Guide: Molecular Cloning, Lambda Phage, Recombinant Dna
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BIO130H1 Full Course Notes
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Document Summary
Recombinant dna: molecules with dna sequences derived from more than 1 source. Type ii restriction endonucleases/restriction enzymes: nucleases that recognize short nucleotide sequences within duplex dna, cleave backbone at specific sites on both strands. Function in bacteria to destroy viral dnas, restricting growth of viruses. Bacterium protects own dna from nucleolytic attack by methylating bases as susceptible sites (chemical modification that blocks action of enzyme) Sequences recognized 4-6 nucleotides long, characterized by internal symmetry. Segment has twofold rotational symmetry (rotated 180 without change in sequence), palindrome. When ecori attacks, breaks each strand at same site in sequence (arrows) Red dots: methylated bases in sequence that protect host dna from enzymatic attack. Some restriction enzymes cleave bonds directly opposite one another on 2 strands producing blunt ends, others make staggered cuts. Allows dna to be dissected into set of specific fragments: once dna digested with enzyme, fragments fractionated on basis of length by gel electrophoresis.
