ABOUT THE ORIGIN OF INTRONS
The origin and functional significance of spliceosomal introns are one of the main mysteries of molecular evolution. Many aspects of the evolution of spliceosomal introns remain unresolved, including the time of their origin, proliferation, mechanisms of acquisition of some introns and loss of others, driving mechanisms of evolution of introns. The article discusses the hypotheses of the “exon theory of genes”, “early introns” and “late introns”, the hypothesis of the origin of LECA (Last Eukaryote Common Ancestor), the time and mechanisms of the emergence of spliceosomal introns, the role of Alu repeats in the formation of introns in humans and higher primates, the role of SINE (Short interspersed nuclear element) and LINE (Long interspersed nuclear elements) of elements, hydrogenosomes, mitosomes, nuclear vesicles and kinetoplast-like organelles Entamoeba histolytica (EhkOs) in the formation of genomes of higher eukaryotes. The data on the average number of splicosome introns in the genes of representatives of different phylogenetic groups of eukaryotes are presented. New original data on the 100% homology of the first intron of the ATP5Po gene (alternative name OSCP is the fifth subunit of ATP synthase or the o subunit that determines the sensitivity to oligomycin) of a human and a fragment of the cytochrome oxidase subunit 1 ( COI ) gene of the non-parasitic shell-borne spates mite Trichoribates sp . from the family Haplozetidae . A new hypothesis is put forward for the origin of eukaryotic splicmosome introns, which consists in the fact that at the early stage of evolution the genomes of many, including unknown protoorganisms, were combined, their orthologous genes recombined, but some of them could not be normally translated due to inconsistencies in the protein synthesizing apparatus. To prevent them from interfering with the normal expression of the entire genome, these genes had to be isolated. Perhaps at this stage of evolution, slicemosomes arose and splicemosome introns already existed in LECA, and the nuclear apparatus itself arose as a defense against the unrestrained expansion of genes requiring different tables of the genetic code for their translation (1 figure, bibliography: 16 refs).