The recent availability of the chicken genome sequence poses the question of whether there are human protein-coding genes conserved in chicken that are currently not included in the human gene catalog. Here, we show, using comparative gene finding followed by experimental verification of exon pairs by RT–PCR, that the addition to the multi-exonic subset of this catalog could be as little as 0.2%, suggesting that we may be closing in on the human gene set. Our protocol, however, has two shortcomings: (i) the bioinformatic screening of the predicted genes, applied to filter out false positives, cannot handle intronless genes; and (ii) the experimental verification could fail to identify expression at a specific developmental time. This highlights the importance of developing methods that could provide a reliable estimate of the number of these two types of genes.

This research is supported by grants BIO2000-1358-C02-02 from ‘Plan Nacional de I+D’ (Spain), Jérôme Lejeune, Childcare and Désirée and Niels Yde Foundations (Switzerland), the European Union Biosapiens Network of Excellence, the Swiss National Science Foundation and the NCCR Frontiers in Genetics. Funding to pay the Open Access publication charges for this article was provided by grant BIO2000-1358-C02-02 from ‘Plan Nacional de I+D’ (Spain).