THE PECULIARITIES OF THE CHROMOSOME ORGANIZATION IN MEIOSIS
T.M. Grishaeva, V.E. Spangenberg, O.L. Kolomiets, S.Ya. Dadashev, Yu.F. Bogdanov
N.I. Vavilov Institute of General Genetics of RAS, Moscow;
e-mail: grishaeva@vigg.ru
Meiotic and mitotic chromosomes differ in a number of features. 1) At the early prophase I of meiosis, chromosomes acquire proteinaceous axial elements (AEs) which were
absent at mitosis. In addition to somatic cohesins, AEs contain meiosis-specific cohesins REC8, SMC1β, STAG3. 2) At the middle prophase I, proteinaceous lateral elements
(LEs) of synaptonemal complexes (SC) are shaped on a basis of AEs. Proteins of LEs are not conserved, but in Saccharomyces cerevisiae and Arabidopsis thaliana
they contain functional domains with conserved secondary structure. Proteins or functional domains similar to SC proteins were found in green and brown algae, some of the lower
fungi and in Coelenterata amongst about 679 hundreds of proteins of primitive eukaryotes studied with bioinformatic methods. 3) During the pachytene and diplotene stages of meiosis
chromosomes of spermatocytes and mother pollen cells acquire the structure reminiscent in miniature the structure of amphibian and avian lamp brush chromosomes. Lateral chromatin
loops of 90, 160 and more than 480 Kb in size are observed in human spermatocytes during the diplotene stage. These findings in sum support the idea of considerable conservation of the
scheme of molecular and ultrastructural organization of meiotic chromosomes in a variety of eukaryotic organisms.
Key words: meiosis, cohesins, synaptonemal complexes, áåëêè, lateral chromatin loops
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