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The modern concept of intercalary heterochromatin as polytene chromosome regions exhibiting a number of specific characteristics is formulated. DNA constituting these regions is replicated late in the S period; therefore, some strands of polytene chromosomes are underrepresented; i.e., they are underreplicated. Late-replicating regions account for about 7% of the genome; genes are located there in clusters of as many as 40. In general, the gene density in the clusters is substantially lower than in the main part of the genome. Late-replicating regions have an inactivating capacity: genes incorporated into these regions as parts of transposons are inactivated with a higher probability. These regions contain a specific protein SUUR affecting the rate of replication completion.

The primary structure of the coat protein (CP) gene was examined for pathogenic strain MS-1 and vaccine strain VIROG-43M of the cucumber green mottle mosaic virus (CGMMV). In CP amino acid composition, strains MS-1 and VIROG-43M are typical representatives of CGMMV: their CPs have 98-100% homology to CPs of other tobamoviruses of the group. The CP gene has the same nucleotide composition in pathogenic MS-1 and vaccine VIROG-43M, indicating that strain attenuation is not determined by this gene. The CP amino acid sequences of the two Russian strains are fully identical to the CP sequences of two Greek strains, GR-3 and GR-5. However, the nucleotide sequences of their genes differ in 13 bp, testifying to the difference between the Russian and Greek strains.

A significant portion of a eukaryotic genome is silent (epigenetically repressed). In Drosophila melanogaster, this portion includes mainly regions of pericentric and intercalary heterochromatin and euchromatin regions subject to position-effect variegation. Detailed study of the organization of intercalary heterochromatin regions of Drosophila melanogaster polytene chromosomes started from the discovery of the SuUR gene (Suppressor of UnderReplication). The ability of the SuUR mutation to suppress underreplication in intercalary heterochromatin regions was used for molecular tagging of these regions. We showed that underreplicated intercalary heterochromatin regions contained silent unique genes and retained the features of late replication and transcriptionally inactive chromatin state in various cell types. Over 50% of these regions contain unique genes clustered on the base of coordinated expression. The origin of clusters and putative mechanisms of their gene expression are discussed. Data on the SuUR gene, its expression, and effect on polytene chromosome structure and replication are summarized.

In a group of patients with endometriosis and in a control group of healthy women, the polymorphism of the following systems were studied: ABO and RH blood-group systems; serum proteins haptoglobin (HP), transferrin (TF), vitamin D-transporting protein (GC), protease inhibitor (PI), and the third component of the complement (C3); serum enzymes-amylase of the loci 1 and 2 (AMY1 and AMY2), pseudocholinesterase (E2), and alkaline phosphatase (PP); erythrocytic enzymes-acid phosphatase (ACP1), phosphoglucomutase (PGM1), superoxide dismutase (SOD-A), esterase D (ESD), and glyoxalase (GLO1). Statistically significant differences between the groups compared were established for five genetic systems: ABO, E2, C3, TF, and PGM1. Among patient with endometriosis, the rare alleles of the locus ESD-ESD5 and ESD7-were found, along with ESD 5-5 homozygotes. Several genetic loci can be involved in the pathogenesis of endometriosis; their products can be specifically realized due to peculiarities of biochemical reactions in the organisms of people predisposed to this pathology.