title: On the origin of distribution patterns of motifs in biological networks.
abstract: BACKGROUND
  Inventories of small subgraphs in biological networks have identified commonly-recurring patterns, called motifs. The inference that these motifs have been selected for function rests on the idea that their occurrences are significantly more frequent than random.
  
  
  RESULTS
  Our analysis of several large biological networks suggests, in contrast, that the frequencies of appearance of common subgraphs are similar in natural and corresponding random networks.
  
  
  CONCLUSIONS
  Indeed, certain topological features of biological networks give rise naturally to the common appearance of the motifs. We therefore question whether frequencies of occurrences are reasonable evidence that the structures of motifs have been selected for their functional contribution to the operation of networks.
authors.affiliation: The Huck Institute for Genomics, Proteomics, and Bioinformatics, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA. arun@bx.psu.edu
authors.forename: Arun S
authors.initials: AS
authors.lastname: Konagurthu
authors.forename: Arthur M
authors.initials: AM
authors.lastname: Lesk
mesh_terms: D004926:Escherichia coli / Q000235:genetics; D053263:Gene Regulatory Networks; D006624:Hippocampus / Q000166:cytology; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D015398:Signal Transduction