Replacement of chromosome segments with altered DNA sequences constructed in vitro.

We have developed a method that may be of general application for the stable introduction of foreign sequences or deletions, constructed in vitro, into the chromosomes of Saccharomyces cerevisiae. No vector sequences are present in the final strains. Ability to transform cells with DNA, availability of a single selective marker, and integration of the transforming DNA by homologous recombination into the chromosomes are the requirements of the system. Any isolated gene can be deleted or altered and then be used to replace the wild-type chromosomal copy. An internal deletion mutant of the his3 gene and a transposition of a galactose-inducible region into chromosome XV have been generated by using the ura3 gene as the selective marker.