It is found that approximately 15-20% of non-coding part of human DNA is constitutive heterochromatin. There are two types of constitutive heterochromatin: C- and Q-heterochromatin. C-heterochromatin regions (C-HRs) are found in the genome of all higher eukaryotes, while Q-heterochromatin regions (Q-HRs) are only in the genome of three higher primates (Homo sapiens, Pan troglodytes and Gorilla gorilla). Human chromosomes possess both types of constitutive heterochromatin. In man C-heterochromatin is present in all his chromosomes, varying mainly in size, while Q-heterochromatin can only be detected on seven autosomes and the Y-chromosome. In this case individuals in a population differ from each other on the number, location, size and intensity of staining (fluorescence) of chromosomal Q-HRs. However, the question of possible biological role of chromosomal Q-HRs in human life remains open. A hypothesis that amount of Q-HRs in genome is possibly connected with human body thermal conductivity (BHC) has been proved. Results obtained show that individuals in population truly differ from each other in BHC and its level depends on the amount of chromosomal Q-HRs in human genome. The question of place and possible role of human BHC in norm and pathology is also being discussed.

Red squirrels (Sciurus vulgaris) are widely distributed throughout Eurasia, occurring in many types of coniferous and mixed-deciduous forests. Even though red squirrels are biologically and genetically well-studied worldwide, so far no genetic studies have been conducted in Mongolia. In this paper, complete sequences of the mitochondrial cytochrome b gene of the Mongolian red squirrel (Sciurus vulgaris) were analyzed to determine genetic diversity. Fifteen specimens were collected from seven provinces: Bulgan, Selenge, Tuv, Khuvsgul, Arkhangai, Zavkhan and Bayan-Ulgii. Ten haplotypes were observed from 15 specimens in seven Mongolian provinces, and the maximum Tamura-Nei nucleotide distance among them was 1.1%, indicating that genetic diversity of Sciurus vulgaris is moderate. The population in Khuvsgul showed the highest genetic distance compared to individuals the remaining populations in Mongolia. Further analyses of mtDNA cytochrome b gene with additional specimens of red squirrels from Khuvsgul province are needed to clarify the reason of environmental condition influencing the genetic variation in the squirrel’s population in Khuvsgul.