[The coevolutionary aspects of the genome and mobile elements]

Under investigation is congruent variation of movable elements, the "genome parasites" (GP), and genome proper, as the "host". Several differential equations are studied that describe the following situations. 1. GP is able to insert in free sites only, existing in autonomous stage (outside of the genome) limited time only. 2. GP inserts in free sites only, being able to exist autonomously relatively long time. 3. GP inserts in both free and occupied sites ("molecular memory"), existing autonomously relatively short time, its prototype being Alu-like repetitions in mammals. 4. GP inserts in both free and occupied sites, and is able to live autonomously, its prototype being retrovirus. In is presumed that the genome is tolerant to "selfish" breeding of GP as long as proportion of invaded sites does not exceed some critical value. It is shown that co-evolutionary complication of GP--from the simplest one that is able to insert in free sites only, through acquiring terminal repetitions ("molecular memory"), up to complicated entities existing outside of genome--accompanied by alteration of selective co-evolutionary limitations on genome size: limitations from above--no limitations--limitations from below. Thus, genetical movable elements can be considered as intrinsic factor of progressive, co-evolutionary stipulated complication of the genome.