[Comparative analysis of patterns of localization of mobile genetic elements in genetic selection experiments on Drosophila melanogaster]

Abstract

A comparative selection-genetic analysis of three heterogeneous lines of Drosophila melanogaster with an interrupted longitudinal wing vein was performed. In the control line, riC, and two selection lines, riSP and riSN, overall patterns of localization of six families mobile genetic elements (MGE) (MGE) (MDG1, MDG2, MDG3, MDG4, copia, and 297) were compared. In all, the lines contained 220 sites (copies) in 153 segments of the Bridges' map. According to response to selection, six classes of sites were identified: strong positive (P), weak positive (p), neutral (n), weak negative (n), strong negative (N), and abnormal (A). More than 50% of the sites (P+N+p+n) were shown to respond to selection; the contrasting classes (P and N and p and n) counterbalanced each other. These sites are assumed to mark actual parts of the genome, where polygenes are located. In other words, more than 50% of the total number of the genome sites act as polygenes controlling this quantitative character and respond to selection. Pleiotropy of polygenes in such a system must be very high. 22.2% of sites are neutral (class 0); apparently, they do not mark polygenes. The remaining 21.8% of sites (class A) show an anomalous response to selection. They are assumed to mark the polygenes of another genetic system, which participated in the maintenance of homeostasis in the original line riC. On the basis of this evidence, the concept of oligogenes and polygenes is developed. Oligogenes and polygenes are genes that occupy respectively limiting and nonlimiting positions in systems of expression. Adaptive properties of oligogenes are evaluated first and evolve rapidly. Adaptive properties of polygenes are evaluated only with regard to their total set and are limited by oligogenes. Variation of polygenic systems is generated by polygenic combination and spontaneous transpositions and excisions of MGE.