The characteristics of chromosomal distribution and of the variability of the multiply repeating DNA fraction of the genome in Bos taurus L.]

The uniform distribution of satellite DNA II and IV has been revealed using in situ hybridization and differential staining in centromeric regions of autosomes. The sex chromosomes have not found such nucleotide blocks. There is only minor satellite IV block inside Y chromosome short arm. The Y chromosome has got some (TG)n enriched blocks distributed also among other parts of genome and one copy of sequences like human ZFY gene. The high repetitive fraction of bovine genomic DNA have not revealed RFLP. However, the difference has been found by blot hybridization between genomic organization of satellite IV in cattle and yak chromosomal DNA. Non-Mendelian distribution of some such nucleotide blocks has been obtained for interspecies crosses of cattle and yak.     

Role of the structural context in selection of hydrophobic side-chain rotamers in a- and d-positions of alpha-helices

The study shows that in coiled-coil proteins the distribution of hydrophobic side-chain rotamers in a- and d-positions of alpha-helices is strongly dependent on the mutual arrangement of the a-helices. In coiled-coil dimers, where a-helices are packed "face-to-face", most side chains occupying a-positions adopt t-rotamers, and those in d-positions adopt g- -rotamers. In tetramers, where alpha-helices are packed "side-by-side", most side chains in a-positions adopt g- -rotamers and those in d-positions adopt t-rotamers. These features can be used for prediction of side-chain rotamers in protein modeling and design.     

The specific blocks of heterochromatin on metaphase chromosomes of horse and Prjewalski horse detected by in situ digestion with restriction endonucleases

Restriction endonuclease in situ digestion of metaphase chromosomes gives an opportunity to reveal strips with different structure within GC-rich pericentric heterochromatin of the domestic horse and the wild Przewalski horse. Blocks of heterochromatin, which are insensitive to HaeIII and brightly stained with chromomycin A3 after restriction enzyme digestion, are localized on the border with euchromatin in the majority of chromosomes of Equus caballus and E. przewalskii. In contrast to chromosome 5 of E. caballus, acrocentric chromosomes of E. prezewalskii which are homologous to this chromosome have RE-CMA-blocks. We discuss a possible nature of the specific heterochromatin, which is insensitive to restriction enzyme digestion, and its role in the karyotype evolution.