Integrative study on chromosome evolution of mammals, ants and wasps basedon the minimum interaction theory

There is well-known evidence that in many eukaryotes, different species hav e different karyotypes (e.g. n = 1-47 in ants and n = 3-51 in mammals). Alt ernative (fusion and fission) hypotheses have been proposed to interpret th is chromosomal diversity. Although the former has long been accepted, accum ulating molecular genetics evidence seems to support the latter. We investi gated this problem from a stochastic viewpoint using the Monte Carlo simula tion method under the minimum interaction theory. We found that the results of simulations consistently interpreted the chromosomal diversity observed in mammals, ants and wasps, and concluded that chromosome evolution tends to evolve as a whole toward increasing chromosome numbers by centric fissio n. Accordingly, our results support the fission hypothesis. We discussed th e process of chromosome evolution based on the latest theory of the molecul ar structure of chromosomes, and reconfirmed that the fission burst is the prime motive force in long-term chromosome evolution, and is effective in m inimizing the genetic risks due to deleterious reciprocal translocations an d in increasing the potential of genetic divergence. Centric fusion plays a biological role in eliminating heterochromatin (C-bands), but is only a lo cal reverse flow in contrast to the previously held views. (C) 2001 Academi c Press.