Chromosomal Q-heterochromatin regions in the indigenous population of the northern part of West Siberia and in new migrants

The variability of Q-heterochromatin regions (Q-HR) was studied in native residents of the northern part of West Siberia, viz Yakuts (n = 127), Selkups (n = 90) and Khants (n = 54), as well as in newcomers including oil-borers (n = 43) and children (n = 113) living permanently in this part of the USSR. The major quantitative characteristics of chromosomal Q-HR variability were shown to be very similar in oil-borers and natives, and this is considered to be the result of specific selection of individuals according to the amount of Q-HRs in their genome. The hypothesis on the possible selective value of chromosomal Q-HRs in human adaptation to extreme environmental conditions of the extreme north is discussed.     

The relationship between the Y chromosome size and the amount of autosomal Q-heterochromatin in human populations

The relationship between the basic quantitative characteristics of the Q-heterochromatin (Q-HR) region variability of autosomes and of the Y chromosome in human populations was examined. A definite relationship between the mean number of Q-HR per individual, the distribution and frequencies of Q-HR on autosomes and the size of the Q-heterochromatin segment of the Y chromosome at the population level was shown to exist. The amount of autosomal Q-HR was lower in individuals with larger Q-heterochromatin segments on Y chromosomes, and vice versa. The hypothesis that the amount of chromosomal Q-HR in the genome of modern human populations may be under the control of natural selection, is discussed.     

The origin of modern humans: A cytogenetic model

A new model of the origin of man is proposed on the basis of recent studies on cytogenetics of chromosomal Q-heterochromatin regions (Q-HRs) in man and other higher primates. This model is based on the following facts: a) chromosomal Q-HRs were found in the genome of only three higher primates (man, the chimpanzee and the gorilla); b) chromosomal Q-HRs in the human genome, unlike those in apes, exhibit considerable quantitative variability; c) the number of human chromosomal Q-HRs in the genome has a selective value in the adaptation of human populations to various environmental conditions. According to this model, the three major morphofunctional distinctions of man—great physiological flexibility, characteristic morphological structure, and conceptual thinking—arose as a result of the capacity of our remote ancestors to broadly change their genome mass owing to features of chromosomal Q-HRs that are only intrinsic to man. We feel that genome-mass variability through chromosomal Q-HRs allowed man to adapt himself to various environments over such a short period of time.     

Human chromosomal polymorphism

Summary Chromosomal Q polymorphism was studied in 157 adolescents of Yakut nationality (67 males and 90 females) living in Eastern Siberia, on the territory of the Yakut ASSR. Of the 157 subjects, 123 had chromosomal Q variants while 34 (21.7%) had no Q-heterochromatin bands with fluorescence levels 4 and 5. The mean number of Q variants per individual ranged from 0 to 5, with a mean of 1.64. No differences were observed in the frequency of Q variants between sexes. The observed homo- and heteromorph frequencies always agreed with those predicted by the law of Hardy-Weinberg. Of the 157 subjects, four (2.55%) had pericentric inversion of the Q-heterochromatin band in chromosome 3. The following topics are discussed: (1) possible selective value of chromosomal Q-heterochromatin material in the adaptation of human populations to extreme environmental factors, in particular to cold; (2) the taxonomic value of chromosomal Q polymorphism in ethnic anthropology.     

Human chromosomal polymorphism. III. Chromosomal Q polymorphism in Mongoloids of northern Asia

Summary Q-heterochromatin variants in seven autosomes (3, 4, 13–15, 21, 22) were studied in two Mongoloid populations of northern Asia (Chukchi and Khakass). Q-staining was obtained using propylquinacrine mustard. Of 132 Chukchi individuals aged 13 to 20 years, 124 had Q-polymorphic chromosomes, while eight (6.0%) had no bands with fluorescence levels 4 and 5. The mean number of Q variants was 2.2 per individual.Of the 120 Khakass individuals aged 14 to 17 years, 112 had Q-polymorphic chromosomes, while eight (6.7%) had no Q variants with fluorescence levels 4 and 5. The mean number of Q variants was 2.5 per individual. No differences were found in the frequency of Q variants between sexes in the two populations. There was complete agreement between the observed homo-and heteromorphic frequencies and those predicted by the law of Hardy-Weinberg. As the Mongoloid populations of northern Asia showed statistically significant homogeneity both in the frequency of Q variants and the distribution of homo-and heteromorphic variants, they were examined as a single group—that of northern Mongoloids. The following questions are discussed: (1) the possible selective value of chromosomal Q-heterochromatin material in the adaptation of human populations to certain extreme environmental factors, in particular to cold and hypoxia; (2) the intraracial heterogeneity of Asian Mongoloids; (3) the taxonomic value of chromosomal Q polymorphism in ethnic anthropology.     

Genetic studies of an apoA-I lipoprotein variant

Summary Chromosomal Q polymorphism was studied in 116 Turkmen, aboriginals of the Kara-Kum desert of Central Asia. Propylquinacrine mustard was used as fluorochrome. Of the 116 subjects aged 16–20 years, 109 (94.0%) were found to have Q-polymorphic variants, while seven (6.0%) showed complete absence of Q bands with fluorescence levels 4 and 5. There was a total of 351 polymorphic Q bands, 0–7 per individual, with a mean of 3.0 in the population. No differences between sexes were observed in the frequency of Q bands. The observed homo- and heteromorph frequencies proved to be in complete agreement with those predicted by the law of Hardy-Weinberg. Chromosome 3 with pericentric inversion of the Q-heterochromatin band was found in two (1.7%) of the 116 subjects.The following questions were examined: (1) the possible selective value of chromosomal Q-heterochromatin material in the adaptation of human populations to extreme environmental factors, in particular to the desert climate; (2) intracial heterogeneity in Europoids of Eurasia; (3) the taxonomic value of Q polymorphism in ethnic anthropology.     

Human chromosomal polymorphism. VII. The distribution of chromosomal Q-polymorphic bands in different human populations

The distribution of chromosomal Q-polymorphic bands was studied in different human populations. The populations studied showed no differences in the relative amount of Q bands in all the 12 polymorphic loci of seven autosomes, but interpopulation differences did exist in the absolute amount of Q bands in all the 12 potentially polymorphic loci of seven autosomes, these differences consisting of uniform increases or decreases in this absolute amount. Comparisons of the mean number of Q-heterochromatin bands with fluorescence levels 4 and 5 per individual showed a consistent prevalence of this quantitative parameter of chromosomal Q polymorphism in females as compared to males in all the national groups. It is suggested that there is some dosage compensation of chromosomal Q-heterochromatin material in females due to the absence of a chromosome in their genome, which is able to "compensate" for the large Q band in chromosome Y which is present only in the karyotype of males.     

Human chromosomal polymorphism. V. Chromosomal Q polymorphism in African populations

Summary The distribution pattern of Q-heterochromatin variants in seven autosomes (3, 4, 13–15, 21, and 22) was studied in three aboriginal Negroid populations of Africa (Mozambique, Angola, and Ethiopia). It was shown that among African Negroids there are no individuals completely lacking Q-heterochromatin bands with fluorescence levels 4 and 5. The mean number of Q variants per individual was 3.47, 4.80, and 4.85 in the Ethiopian, Mozambique, and Angola populations, respectively. The observed homo- and heteromorphic frequencies always agreed with those predicted by the law of Hardy-Weinberg. The populations of tropical lowland Negroids (Mozambique and Angola) proved to be significantly homogeneous both in the frequency of Q variants and the mean number of these variants per individual, so they were examined as a single group. However, comparative analysis of highland (Ethiopians) and lowland Negroids revealed statistically significant differences. The following questions are discussed: (1) the possible selective value of chromosomal Q heterochromatin material in the adaptation of human populations to high-altitude climate; (2) the possible existence of intraracial heterogeneity in Negroids living in different ecological zones of Africa; (3) the possible taxonomic value of an inverted Q-heterochromatin band in chromosome 3 in ethnic anthropology.     

Biological invasions and climate change amplify each other’s effects on dryland degradation

Climate models predict that, in the coming decades, many arid regions will experience increasingly hot conditions and will be affected more frequently by drought. These regions are also experiencing rapid vegetation change, notably invasion by exotic grasses. Invasive grasses spread rapidly into native desert ecosystems due, in particular, to interannual variability in precipitation and periodic fires. The resultant destruction of non-fire-adapted native shrub and grass communities and of the inherent soil resource heterogeneity can yield invader-dominated grasslands. Moreover, recurrent droughts are expected to cause widespread physiological stress and mortality of both invasive and native plants, as well as the loss of soil resources. However, the magnitude of these effects may differ between invasive and native grasses, especially under warmer conditions, rendering the trajectory of vegetated communities uncertain. Using the Biosphere 2 facility in the Sonoran Desert, we evaluated the viability of these hypothesized relationships by simulating combinations of drought and elevated temperature (+5°C) and assessing the ecophysiological and mortality responses of both a dominant invasive grass (Pennisetum ciliare or buffelgrass) and a dominant native grass (Heteropogan contortus or tanglehead). While both grasses survived protracted drought at ambient temperatures by inducing dormancy, drought under warmed conditions exceeded the tolerance limits of the native species, resulting in greater and more rapid mortality than exhibited by the invasive. Thus, two major drivers of global environmental change, biological invasion and climate change, can be expected to synergistically accelerate ecosystem degradation unless large-scale interventions are enacted.     

Human chromosomal polymorphism. I. Chromosomal Q polymorphism in Mongoloid populations of central Asia

Summary A comparative study of frequencies and types of Q-polymorphic variants in seven autosome pairs (3, 4, 13–15, 21, and 22) was performed in three steppe Mongoloid populations of Central Asia (Kazakhs, Dunghans, Mongolians) and three highland Kirghiz populations of Pamir and Tien-Shan. The three steppe Mongoloid populations showed statistically significant homogeneity both in the frequency of Q-polymorphic variants and the distribution of homo- and heteromorphs, with complete agreement of observed frequencies with those theoretically predicted by the law of Hardy-Weinberg. Similar homogeneity was revealed in the three highland Kirghiz populations of Pamir and Tien-Shan. However, comparative analysis of highland and steppe Mongoloids revealed significant differences in the following variables: (1) mean number of Q variants per individual, 2.50 and 3.49 in the highland and steppe populations, respectively; (2) frequency of Q variants in 7 of the 12 autosomes studied; and (3) distribution of homo- and heteromorphs in four autosomal pairs (13–15, 21) with a preponderance of individuals with increased homomorph (-/-) frequency in highlanders.The following questions are discussed: (1) the possible selective value of chromosomal Q-heterochromatin material in the adaptation of human populations to extreme environmental factors, in particular to the high-altitude environment of Pamir and Tien-Shan; (2) the existence of intraracial heterogeneity in Mongoloids living in different ecological zones; and (3) the possible taxonomic value of Q-variant inversion in chromosome 3.     

Implications of copy number variation in people with chromosomal abnormalities: potential for greater variation in copy number state may contribute to variability of phenotype

Copy number variation is common in the human genome with many regions, overlapping thousands of genes, now known to be deleted or amplified. Aneuploidies and other forms of chromosomal imbalance have a wide range of adverse phenotypes and are a common cause of birth defects resulting in significant morbidity and mortality. “Normal” copy number variants (CNVs) embedded within the regions of chromosome imbalance may affect the clinical outcomes by altering the local copy number of important genes or regulatory regions: this could alleviate or exacerbate certain phenotypes. In this way CNVs may contribute to the clinical variability seen in many disorders caused by chromosomal abnormalities, such as the congenital heart defects (CHD) seen in ~40% of Down’s syndrome (DS) patients. Investigation of CNVs may therefore help to pinpoint critical genes or regulatory elements, elucidating the molecular mechanisms underlying these conditions, also shedding light on the aetiology of such phenotypes in people without major chromosome imbalances, and ultimately leading to their improved detection and treatment.     

The ecophysiology of apple snails in rice: implications for crop management and policy

This review relates the ecology and physiology of apple snails (Ampullariidae) to their impact on rice‐production systems. Two species in particular, Pomacea canaliculata and Pomacea maculata, have been introduced to several rice‐growing regions. Flooded rice systems represent a high‐quality habitat for these apple snails because of similarities in the environmental conditions (water temperature, salinity, pH, water flow velocity) necessary for both rice production and for snail survival and development. Furthermore, amphibious respiration, a capacity to aestivate during dry periods, as well as cold acclimation and tolerance (particularly in P. canaliculata), increases the resilience of apple snails to rice farming practices, including agrochemical applications, intermittent drainage and crop rotations – under a wide range of climatic conditions. Risks to regional rice production depend on four principal factors: these are (a) regional climate, (b) regional rice‐production systems, (c) prevailing production practices, and (4) the presence/absence of invasive, non‐native apple snails. Based on these criteria, lowland irrigated rice in tropical and subtropical regions that is wet‐direct seeded is most vulnerable to damage from both native and non‐native apple snails (albeit with greater losses from non‐native snails because of normally higher densities). Adequate quarantine regulations, particularly in vulnerable tropical regions that are adjacent to centres of recent outbreaks (e.g. India and Bangladesh adjacent to Myanmar, Peru and Colombia adjacent to Ecuador) and attention to the preparedness of farming systems could reduce potential impacts as these highly invasive snails continue to spread. The urgent development of labour‐saving crop‐establishment methods that reduce dependencies on chemical molluscicides is necessary to achieve sustainable rice production in regions at risk from non‐native apple snails.     

The ultrastructure and properties of centromeric heterochromatin in cultured bovine trachea cells]

The fine organization of the centromere structural heterochromatin (CSH) in a cell culture of calf trachea (TR) was studied by the methods of light and electron microscopy after fixation in native conditions and after treatments with water Henk's solutions and solutions of Ca2+ of different concentrations. In interphase nuclei the CSH forms compact blocks--the chromocentres, which are connected with the nuclear envelope or the nucleolus. The diameter of the main class of DNP fibers in the CSH, chromosomal arms and chromocentres after fixation of control cells and after treatment with 50% Henk's solution is 20-25 nm. 10-15 nm DNP fibers are largely found in the contacts with kinetochores. After 20% Henk's solution treatment 10-15 nm fibers predominate in the CSH and chromosomal arms. A chromonema--a 100 nm chromatin fiber--is detected in the CSH after treatments with different concentrations of Ca2+ solutions, as well after fixation in native conditions. The peculiarity of structural organization and properties of the calf CSH at interphase and mitosis as compared with analogous regions in mouse chromosomes are suggested to be connected with the composition of its DNA and proteins.     

Macroecology of global bryophyte invasions at different invasion stages

In this study we provide the first comprehensive assessment of the environmental and anthropogenic factors driving bryophyte invasions worldwide. We compiled data of alien bryophyte distributions from 82 regions on five continents and oceanic islands and region specific variables. For each species, we collected data on its region‐specific invasion stage, i.e. casual (ephemeral) vs naturalized (persistent) occurrences, and we differentiated between known aliens and those which are likely to be alien (cryptogenic). We used these data to test how species attributes, environmental and socio‐economic conditions of the study areas as well as introduction effort affect invasion probabilities at different invasion stages and of known alien vs cryptogenic species. We collected information on species’ attributes (native range size and location, niche breadth, habitat affiliation), and calculated variables characterising the environmental, biogeographic and socio‐economic features of the native and recepient regions. Subsequently, we related the probability of alien occurrence across different invasion stages with these species‐ and region‐wise predictor variables using generalized linear mixed effects models. Greater native range size raised the likelihood that a species becomes alien or cryptogenic. Islands are more invaded by alien (and cryptogenic) bryophytes than continental regions. Native range size and socio‐economic activity increase the likelihood that a species becomes alien or cryptogenic elsewhere. Interestingly, among alien bryophytes naturalizations occur more frequently in regions of the complementary hemisphere than in regions of their native hemisphere. In general, regions in the Southern Hemisphere have higher numbers of naturalized bryophytes. We conclude that there is a conspicuous change in factors determining bryophyte invasions at different invasion stages. Whereas alien and cryptogenic bryophyte species occurrences are more frequent on islands and depend on native range size, and hence probably propagule pressure, naturalized bryophytes are more frequent in areas which are biogeographically separated but climatically similar to the native ranges.     

Genetic regulation of bone mineral density in mice

Peak bone mass is a major determinant of risk of osteoporotic fracture. Family and twin studies have found a strong genetic component to the determination of bone mineral density (BMD). However, BMD is a complex trait whose expression is confounded by environmental influences and polygenic inheritance. The number, locations and effects of the individual genes contributing to natural variation in this trait are all unknown. The extreme difficulty of dissecting out environmental factors from genetic ones in humans has motivated the investigation of animal models. Genetically distinct animal strains raised under strict environmental control are critical tools for defining genetic regulation. The availability of inbred strains, combined with its relative fecundity, has established the mouse as the best model system for the study of mammalian genetics and physiology. Importantly, genes identified in murine analyses can usually be readily mapped to particular human chromosomal regions because of the high degree of synteny that exists between the mouse and human genomes. We employed quantitative trait locus (QTL) analysis to examine peak BMD in 24 recombinant inbred (RI) mouse strains, derived from a cross between C57BL/6 (B6) and DBA/2 (D2) progenitors (BXD RI). The distribution of BMD values among these strains clearly indicated the presence of strong genetic influences, with an estimated narrow sense heritability of 35%. The differences in peak whole body BMD in the BXD strains were integrated with a large database of genetic markers previously defined in the RI BXD strains to generate chromosome map sites for QTL locations. This QTL analysis provisionally identified a number of chromosomal sites linked to BMD. In the second phase of our BMD QTL mapping efforts, we used three independent mouse populations (all derived from B6 and D2 progenitor strains) to confirm and narrow the genetic locations of 4 QTLs (on chromosomes 1, 2, 4, and 11) that strongly influence the acquisition of peak BMD in mice. Using a novel, fine-mapping approach (recombinant inbred segregation testing), we have succeeded in narrowing two of the BMD-related chromosomal regions and in the process eliminated a number of candidate genes. The homologous regions in the human genome for each of these murine QTLs have been identified in recent human genetic studies. In light of this, we believe that findings in mice should aid in the identification of specific candidate genes for study in humans.     

Phenotypic plasticity and between population differentiation in <Emphasis Type="Italic">Iris pumila</Emphasis> transplants between native open and anthropogenic shade habitats

Response to environmental heterogeneity caused by human activity was analyzed on Iris pumila reciprocal transplants between native steppe and anthropogenic (planted pine forest) habitats that were monitored during several growing seasons in a protected area of Deliblato Sand. Morphometric traits exhibited significant plastic responses to the environmental variability between native and anthropogenic habitats that differed in light quantity and quality, as well as in some other ecological indices. Significant differentiation between populations occupying those habitats was also detected. Plastic responses and population differences were substantially related to the variation in general size and had the same direction, plastic responses being larger in magnitude. Estimates of reproductive and vegetative performance of reciprocal transplants detected home site advantage in the native open but not in the secondary shade habitat created under anthropogenic influence.     

Variability in life history parameters of four serotinous plants in the Namib Desert

Plants growing in extreme habitats, such as deserts, are expected to show high plasticity (variability) in life history parameters to compensate for the unpredictability of their environment. In this study variability in life history parameters and possible sources of variability were investigated in four serotinous (= seed retaining) plant species from the Namib Desert.Blepharis grossa, Geigeria alata, Geigeria ornativa andPetalidium setosum were studied in a mosaic of spatio-temporal environmental conditions represented by three sites and three rain seasons. The coefficient of variation and whether or not significant differences occurred between environmental conditions were used to determine the most variable species and parameters. The most variable species was the strictly annualB. grossa, which might be related to its life form strategy and poor competitive ability as a pioneer species. Life history parameters which responded most frequently to varying environmental conditions were source pool, flowering time and seed production. Seedling density was influenced by the source pool and intensity of rainfall, seedling establishment by timing and intensity of rain events, as well as by seed mass. Although it was expected that high within population variability in life history parameters would also result in a response to differing environmental conditions, there was no direct correlation. Variable responses in life history parameters in most species were caused by differences in site condition as well as by differences in seasons, especially with regard to timing and intensity of rain events.