Theconstruction ofcosmid libraries whichcanbeusedtotransform eukaryotic cells

Cosmidvectorshavebeendevelopedwhichcarryselective markers forgrowthinbacteria(,lactamasegene)andanimalcells(theHerpes Simplexvirusthymidine kinasegene,thetransposonTn-5aminoglycosyl 3' phosphotransferase geneandtheE.coliguaninephosphoribosyltransferase gene). Thedesignof thecosmidsallowstheexchangeof theeukaryotic markersinrecombinant cosmids. Humanandmousecosmidlibraries containing DNA insertsof about40kbhavebeengeneratedby an improved method. Severalclonesfromthehuman,3-globin locuswereisolated.These cosmidstransformmouseL cellsathighefficiency inbothcircularand linearform. Thenewlyintroduced genesareexpressedaccuratelyin L cells.