Literature: Network of tRNA Gene Sequences
What is more, the tRNA similarity network behaves scale-free properties when s0 is large. As we know the scale-free nature is rooted in two generic mechanisms. Firstly scale-free networks describe open systems that grow by the continuous addition of new nodes. Secondly scale-free networks exhibit preferential attachment that means the likelihood of connecting to a node depends on the node’s degree. With these mechanisms, the ”very connected” nodes in scale-free networks usually are added in the network at early time during the growth of the network. It has been found that most recent tRNA genes are evolved from a few common precursors[12, 15], and these oldest evolutionary sequences, comparing to the recent tRNA genes. Therefore, in tRNA similarity netwok, the ”very connected” tRNA genes may have diverged less from their ancestors than weakly connected ones.