Distribution of power-law parameter (α) of domain degrees across 77 bigram networks. From the left to the right in the plot, organisms of the x-axis labels are ordered in protista, fungi, plantae and metazoa. In each studied organism, node degree in the bigram network follows a power-law distribution, n(k) ∝ k-α, where n(k) denotes the number of domains having degree k. The value α in the power-law distribution reflects to the overall likelihood that a bigram involving two randomly selected domains may exist. A comparison of α values across the 77 genomes suggests that overall trend that in more complex organisms such as in metazoa and plantae, a domain tends to have more chances to recombine with other domains.
Xie et al. BMC Evolutionary Biology 2011 11:242 doi:10.1186/1471-2148-11-242