Watch out for aneuploidy

In an analysis of both new and old microarray data in the July Nature Genetics, Hughes et al. find that results are frequently skewed by aneuploidy (Nat. Gen. 2000, 25:333-337). Their first clue was an unexpected transcript profile similarity between two unrelated yeast mutants; the cause turned out to be an extra copy of an entire chromosome. Approximately 8% of the yeast mutants examined had chromosome-wide expression biases, even though most of these mutants are not known to have chromosome transmission defects. In five cases a gained chromosome had a close homologue of the deleted gene, and in two cases a growth advantage was demonstrated.