[Mobile elements and evolution].

Mobile elements (ME) represent an important component of the genome of all organisms studied so far. ME belong to two major classes differing by the mechanism of transposition. Class I ME transpose using RNA intermediate and reverse transcriptase, while class II elements encode their own transposase and may transpose by cut and paste mechanism. Intra and intergenomic distribution of various classes of ME is discussed in the review. An important role of various groups of ME in regulation of cellular genes is also documented. The data accumulated enable to suggest that multiple invasions of ME with subsequent amplification in the host genome may significantly contribute to the adaptation of population to drastic changes in environment. Various roles of ME in the evolution of higher organisms including speciation process are discussed.