McGinnis and Lawrence reply

Gehring states that there is documentary evidence that it was he alone of his research group who appreciated that a weak band on Garber's Southern blot of autumn 1982 was the first sign of the homeobox. This evidence consists of the statement in the November 1983 paper of Garber et al.2 that “weak homology was detected between 903 and 909 probes (Antennapedia cDNAs) and position 190 (of the genomic walk that included the Antennapedia transcription unit)”. However, this paper was submitted on 18 July 1983, after the significance of the homeobox cross-hybridization had become clear to everyone in Gehring's lab — but by the different route described in our review.

In July 1983, the status of homeobox research was as follows. A few novel Drosophila homeobox clones had been isolated, and one of these was defined as a 3′ exon of the Ultrabithorax (homeotic) gene. All the novel clones mapped to cytogenetic regions that were known to contain the two homeotic gene clusters in flies. The transcripts encoded in these clones were expressed in unique, homeotic-like stripes on the anteroposterior axis of developing embryos. So, at the time the 1983 Garber paper was written, it was known in Gehring's lab (but only retrospectively) that Garber's band was not an artefact.

It is always possible that Gehring sensed or knew in 1982 that Garber's band was a crucial clue which should be the basis of further investigation. However, to our knowledge no one heard any such suggestion, nothing was done about it, and it did not spark the crucial experiments on the homeobox sequence in Antennapedia and other developmental control genes.