Mutational bias shaping fly copy number variation: implications for genome evolution.

Copy number variants (CNVs) underlie several genomic disorders and are a major source of genetic innovation. Consequently, any bias affecting their placement in the genome will impact our understanding of human disease and genome evolution. Here we report a mutational bias affecting CNVs that generates different probabilities of duplication and deletion across the genome in association with DNA replication time. We show that this mutational bias has important consequences for genome evolution by leading to different probabilities of gene duplication for different classes of genes and by linking the probability of gene duplication with the transcriptional activity of genes.