Rates and patterns of gene duplication and loss in the human genome

Gene duplication has certainly played a major role in structuring vertebrate genomes but the extent and nature of the duplication events involved remains controversial. A recent study identified two major episodes of gene duplication: one episode of putative genome duplication ca. 500 Myr ago and a more recent gene–family expansion attributed to segmental or tandem duplications. We confirm this pattern using methods not reliant on molecular clocks for individual gene families. However, analysis of a simple model of the birth–death process suggests that the apparent recent episode of duplication is an artefact of the birth–death process. We show that a constant–rate birth–death model is appropriate for gene duplication data, allowing us to estimate the rate of gene duplication and loss in the vertebrate genome over the last 200 Myr (0.00115 and 0.00740 Myr–1 lineage–1, respectively). Finally, we show that increasing rates of gene loss reduce the impact of a genome–wide duplication event on the distribution of gene duplications through time.