Creating a Saccharomyces cerevisiae haploid strain having 21 chromosomes.

Chromosome engineering techniques that can manipulate a large segment of chromosomal DNA are useful not only for studying the organization of eukaryotic genomes but also for the improvement of industrially important strains. Toward the development of techniques that can efficiently manipulate a large segment of chromosome, we have previously reported a one-step chromosome splitting technique in a haploid Saccharomyces cerevisiae cell, with which we could successfully split yeast chromosome 11, XIII, or XI into two halves to create a haploid strain having 17 chromosomes. We have now constructed chromosome splitting vectors bearing ADE2, HIS3, LEU2, or TRP1 marker, and by using these vectors, we could successively split yeast chromosomes to create a novel yeast haploid strain having up to 21 chromosomes.