Reducing yeast chromosome numbers has only minor effect on cell fitness

Different species of eukaryote have wildly different numbers of chromosomes, but how tolerant any given species is to variation in that number remains unclear. Now two research groups, led independently by Jef Boeke and Zhongjun Qin, have successively fused yeast chromosomes to produce strains with two chromosomes and one chromosome, respectively. Although the fitness of the engineered cells is mildly diminished in some environments, with sexual reproduction most severely affected, these cells are remarkably healthy, despite major three-dimensional re-organization of the giant chromosomes.