Dna sequencing: there are fundamental techniques in molecular biology. Other more complex techniques borrow from the same general principles underlying dna cloning, pcr and dna sequencing. A: for many traditional molecular biology protocols, a high concentration of the dna fragment or region is required for analysis (ex. dideoxy sequencing) Two frequently used methods to obtain dna fragments for analysis: dna cloning, polymerase chain reaction (pcr) Basic summary: vector + dna fragment, recombinant dna, replication of recombinant dna within host cells, isolation, sequencing, and manipulation of puri ed dna fragment. Restrcition enzymes and dna ligases allow insertion of dna fragments into cloning vectors. Restriction enzymes are endonucleases: restriction endonucleases recognizes a speci c 4-8 bp sequence (ie gaattc) called restriction sites, cleaves phosphodiester bonds in both strands in a symmetrical fashion. Dna fragments with sticky ends can be inserted into a vector.