Genetic engineering: using in vitro techniques to alter genetic material in the laboratory restriction enzymes, gel electrophoresis, nucleic acid hybridization and probes, molecular cloning, cloning vectors. Restriction enzymes: recognize specific dna sequences and cut dna at those sites widespread among prokaryotes, rare in eukaryotes, protect prokaryotes from hostile foreign dna and essential for in vitro (viruses) Three classes of restriction enzymes: type ii cleave dna within their recognition sequence and are most useful for specific dna manipulation. Restriction enzymes recognize inverted repeat sequences (palindromes) typically 4-8 base pairs long. Eco ri is a restriction enzyme that recognizes a 6 base pair sequence that creates a sticky end. Modification enzymes: protect cell"s dna for restriction enzymes chemically modify nucleotides in restriction recognition sequence modification generally consist of methylation of dna. Gels can be stained with ethidium bromide and dna can be visualized under uv light.