Construction of genomic libraries lain why genomic libraries are useful: outline the construction of a genomic library and how the gene of interest might be selected. Identify commonly used host cells: compare two common techniques by which recombinant dna constructed in vitro is introduced into host cells. Inserting recombinant dna into host cells: most common hosts. S. cerevisiae eukaryotic host: hosts are engineered to lack restriction enzymes and reca, dna introduction into microbes transformation. Differences exist in eukaryotic and bacterial hosts. Mrna requires a leader sequence and mrna modifications, intron removal. More foreign gene expression: expression vectors are used to overcome problems with expression of recombinant genes in host cells, contain inducible promoters that result in high-level transcription. Purification and study of recombinant proteins: protein purification isolation of gene product. Polyhistidine tagging (his-tagging) isolation of protein by metal ion resin: fluorescent labeling in vivo expression and regulation.