A theoretical approach to chromosome banding pattern analysis.

Abstract

Based on a schematic model of karyotype evolution, a new methodology for G-, R-, or Q-banding pattern analysis was investigated. Banding pattern analysis essentially depends on the unidirectional alteration and the randomness of the exchange sites of the AM-inversion. In karyotypes that evolved by AM-inversion and Robertsonian rearrangement, two matching patterns appear; (1) tandem and (2) complementary matching patterns. The former is characteristic of a single lineage sharing the same AM-inversions, and the latter appears in different lineages sharing different AM-inversions, by which it is theoretically possible to detect the ancestral karyotype and to reconstruct the karyotype phylogeny (cladogram). In contrast, the evolutionary pathway cannot always be perceived if karyotypes evolve only by Robertsonian rearrangement. The tandem matching pattern does not always mean tandem fusion, but can be interpreted as 'tandem fission' by a combination of AM-inversion and centric fission. Tandem fusion and MM-inversion often cause entangled matching patterns, and thus they interfere with banding pattern analysis. Some methodological problems inherent in the conventional banding pattern analysis are highlighted, and suggested that such problems can be minimized by using the karyograph method. The methodology of banding pattern analysis proposed in the present paper will be applicable for matching the chromosome map of genetic markers among different species.