Following recent technological advances there has been an increasing interest in genome structural variation, in particular copy-number variants (CNVs) – large-scale duplications and deletions – in the human genome. Although not immediately evident, CNV surveys make a conceptual connection between the fields of population genetics and protein families, in particular with regard to the stability and expandability of families. The mechanisms giving rise to CNVs can be considered as fundamental processes underlying gene duplication and loss; duplicated genes being the results of “successful” copies, fixed and maintained in the population. Conversely, many “unsuccessful” duplicates remain in the genome as pseudogenes. Here, we survey studies on CNVs, highlighting issues related to protein families. In particular, CNVs tend to affect specific gene functional categories, such as those associated with environmental response, and are depleted in genes related to basic cellular processes. Furthermore, CNVs occur more often at the periphery of the protein interaction network. Thereby, functional categories associated with successful duplicates and unsuccessful duplicates are clearly distinguishable. These trends are likely reflective of CNV formation biases and natural selection, both of which differentially influence distinct protein families.
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