Distribution of endogenous retrovirus copies in the mouse reference C57Bl/6 genome. The observed distribution of ERV copies is compared with the expected pattern if these elements were randomly distributed. ERV distribution with regard to gene (A) TSSs or (B) TTSs. Arrows indicates the maximum distance between an ERV and a gene that is under negative selection based on our statistical analysis. A proportion equality test allowed us to compare both distributions and uncover significant differences. ***P <0.001, **P <0.01 and *P <0.05. ERV copies can be located upstream, inside or downstream of genes. ERV: endogenous retrovirus; TSS: transcription start site; TTS: transcription termination site.
Rebollo et al. Genome Biology 2012 13:R89 doi:10.1186/gb-2012-13-10-r89