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The densities of aqueous solutions of bisurea (2,4,6,8 tetraazabicyclo[3.3.0]octane 3,7 dione) were measured using a vibrating tube densimeter at 288.15, 298.15, 308.15, and 318.15 K in the concentration range up to ~3•10 -3 moles of solute (1000 g of H 2 O) -1 with the error at most ±5•10 -6 g cm -3 (reproducibility up to 2•10 -6 g cm -3 ). The limiting partial molar volume and expansibility of bisurea in water were calculated. The bicyclic molecules under study form in aqueous solution H bonded hydrate complexes with rather high structure packing density. These complexes are more subjected to the destroying effect of temperature than the corre sponding urea complexes. The hydration of bisurea weakens with the temperature increase.

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The Chinese hamster (Cricetulus griseus) and striped hamster (Cricetulus barabensis) are very closely related species with similar karyotypes. The karyotypes differ from each other by one Robertsonian rearrangement and X-chromosome morphology. The level of the tandem repeat (TR) sequences’ evolutional variability is high. The aim of the current work was to trace the TR distribution on the chromosomes of two very closely related species. The striped hamster genome has not yet been sequenced. We classified the Chinese hamster TR in the assemblies available and then compared the mode of the TR distribution in closely related species. Chinese and striped hamsters are separate species due to the relative species specificity of Chinese hamster TR and prominent differences in the TR distribution in both species. The TR variation observed within homologous striped hamster chromosomes is caused by a lack of inbreeding in natural populations. The set of TR tested could be used to examine the CHO lines’ instability that has been observed in heterochromatic regions.

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