Exon shuffling hotspots in an animal genome

The birth of new genes is key to evolution. Exon shuffling is a powerful mechanism for gene birth in which new genes are made by stitching together fragments of existing ones. I report hotspots of exon shuffling in the genome of the animal Drosophila affinis. These are relatively small regions that quickly receive, concentrate, and rearrange gene fragments from around the genome. I detail the recent creation of transcripts containing composite open reading frames at these hotspots, including cases that resemble not just the birth of a single gene but of gene families. I describe basic phenomenology of the hotspots and propose that they are best described not specifically in terms of exon shuffling but more broadly by their tendency to toy with existing genomic sequences as "tinkering loci." I speculate that tinkering loci may overcome barriers to the reassortment of modular sequences, accelerating animal evolution.