Creating a functional single-chromosome yeast.

The genome of the model yeast organism Saccharomyces cerevisiae consists of 16 chromosomes. Using CRISPR/Cas9 scientists created a yeast strain that contains a single chromosome that was generated by successive end-to-end fusions of the 16 chromosomes and by deletions of the centromeres. It is the first synthetically generated yeast strain that consists of one linear chromosome. Compared to the wild type yeast strain the synthetic yeast strain contains eleven single nucleotide polymorphisms (DNA sequence variations), seven insertions and 28 genes are expressed differentially, which are mostly involved in the stress-response. The strain shows reduced growth, competitiveness, gamete production and viability. Furthermore the 3D chromosome structure is different compared to the wildtype which results from the deletion of the centromeres.