How new genes emerge while others decay could be explained, in part, by an unusual means of gene duplication.

Ichizo Kobayashi at the University of Tokyo and his team compared the complete genome sequences of ten strains of the bacterium Helicobacter pylori, which causes stomach ulcers, from people living around the world. From this, they reconstructed the evolutionary history of the organism's chromosome organization.

Some strains contain a single copy of a host-interaction gene, whereas others have two. The duplicate gene and the DNA between the two have been flipped around. The researchers think that a single process copied the gene while inverting the DNA. In some strains, this mechanism seems to have interrupted a host-interaction gene, causing it to decay, whereas in other strains a new gene has evolved as a result of the process.

The same mechanism could occur in cancer cells, creating abnormal numbers and arrangements of genes, the researchers say.

Proc. Natl Acad. Sci. USA doi:10.1073/pnas.1012579108 (2011)