Nat. Biotechnol. 21, 652–659 (2003)

In the author list, the name of author Rostislav Chernomorsky was misspelled Rostislav Chernomorski. In addition, an acknowledgment was omitted: the authors would like to acknowledge Panos Ioannou for help with early bacterial homologous recombination experiments. The corrected acknowlegments should read: We thank Margaret Karow for intellectual input, Petra Kraus for analysis of gene expression patterns and Fred W. Alt, Craig Bassing, Richard Flavell, Mike Brown, Joe Goldstein, Eric Shooter and Kornelia Polyak for suggesting genes to target. We thank Andrea Elsasser for excellent database design, implementation and support, and Dr. Amalia Dutra for advice and assistance with FISH. We would also like to thank Li Pan, Joyce McClain, Virginia Hughes, Jeffrey Vercollone, Kethi Mullei, Jorge Bermudez, Jennifer Leung, Ning Yuan, Samantha Park, Ruth Santos, Collen Correa, Huan Jiang, Jinsop Om and Youngli Chang for technical assistance, Vicki Lan and Scott Staton for graphics support and Panos Ioannou for help with early bacterial homologous recombination experiments.