Genes are so embedded in our intellectual DNA (to repatriate a fashionable idiom) that we tend to forget that we still have no agreed definition of the term . When we say that there are fewer than 25,000 genes in the human genome , we are thinking of protein-coding sequences, but are the associated introns and regulatory sequences part of the gene? And what about splice variants, untranslated RNAs, epigenetic modifications? These are important aspects of the genetic material and currently hot research topics. Furthermore, genes still occupy a central place in our modern understanding of biology, and all the connections that preoccupied our predecessors a century ago are still lively issues. The explosion of genome data and of new techniques is generating new insights in human diversity, developmental biology, molecular evolution, systems biology and many other directions