[Research on the genetic structure of natural populations of Cepaea nemoralis].
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[Change in the genetic structure of an experimental population of Drosophila by electrophoretic locus under the effect of ecological conditions].
Dynamics of the genetic structure of experimental Drosophila populations being kept over 50 generations at 25 and 17 degrees C6 and on the medium with ethanol (12%) was studied. In all experimental populations alteration in allele frequencies of Adh, Gpdh, Hex and Est-6 loci took place in the first 20-25 generations on monitoring under the influence of the temperature and ethanol. Later on, an equilibrium relation between allele frequencies will be established.
Alcohol Dehydrogenase↗
Assessing genetic structure with multiple classes of molecular markers: a case study involving the introduced fire ant Solenopsis invicta.
We used 30 genetic markers of 6 different classes to describe hierarchical genetic structure in introduced populations of the fire ant Solenopsis invicta. These included four classes of presumably neutral nuclear loci (allozymes, codominant random amplified polymorphic DNAs (RAPDs), microsatellites, and dominant RAPDs), a class comprising two linked protein-coding nuclear loci under selection, and a marker of the mitochondrial DNA (mtDNA). Patterns of structure revealed by F statistics and exact tests of differentiation were highly concordant among the four classes of neutral nuclear markers, although the microsatellites were the most effective markers for detecting structure. The results from the mtDNA complemented those from the neutral nuclear markers by revealing that strong limitations to female-mediated gene flow were the cause of the local structure registered by the nuclear markers. The pattern of structure inferred from the selected nuclear loci was markedly different from the patterns derived from the other sets of markers but was predictable on the basis of the presumed mode of selection acting on these loci. In general, the results for all six classes of markers can be explained by known features of the social and reproductive biology of fire ants. Thus, the results from these diverse sets of markers, combined with detailed natural history data, provide an unusually complete picture of how the fundamental evolutionary forces of gene flow, drift, and selection govern the distribution of genetic variation within and between fire ant populations.
Animals↗
Genetic structure of Indian scad mackerel Decapterus russelli: Pleistocene vicariance and secondary contact in the Central Indo-West Pacific Seas.
Major genetic breaks between the Indian and Pacific oceans have been reported for marine fishes and invertebrates. The genetic structure and history of the Indian scad mackerel, Decapterus russelli, in the Indo-Malay archipelago were investigated using the cytochrome b gene sequence as mitochondrial marker and two length-polymorphic introns as nuclear markers. The existence of two major mitochondrial lineages separated by 2.2% average nucleotide divergence, and their heterogeneous geographical distributions, were confirmed. This indicated past geographic isolation, possibly caused by a Pleistocene drop in sea level. The presence, in sympatry, of the two mitochondrial lineages was thought to result from secondary contact. A recent population bottleneck and subsequent rapid population expansion were indicated by low genetic diversities and strongly negative Tajima's D-values. This evidence supports the hypothesis that the habitat available to D. russelli in the Pleistocene was restricted. Taking into account both mitochondrial and nuclear-DNA data, three geographically distinct populations were identified: one sampled in the Makassar Strait and Sulawesi Sea, one in the Arafura Sea and the third from the entire western region of the Indo-Malay archipelago. Considering the high hydrological connectivity of this region of the Indo-Pacific and the species pelagic life-history, the population structure may be maintained by homing behaviour and, perhaps, the association of spawning with retention zones.
Animals↗
Strong genetic structuring in a habitat specialist, the oxleyan pygmy perch nannoperca oxleyana
This study used allozyme and mitochondrial DNA variation to examine genetic structure in the Oxleyan Pygmy Perch Nannoperca oxleyana. This small-bodied freshwater fish has a very restricted distribution occurring only in some small coastal streams in south-east Queensland and northern New South Wales. It was expected that subpopulations may contain little genetic variation and be highly differentiated from one another. The results, based on allozyme and mitochondrial DNA control region variation were in agreement with these expectations. Allozyme variation was very low overall, with only one locus showing variation at most sites. The high differentiation was because a different locus tended to be polymorphic at each site. Mitochondrial variation within sites was also low, but some sites had unique haplotypes. The patterns of similarity among mitochondrial DNA haplotypes were not as expected from geographical proximity alone. In particular, although some northern sites had unique haplotypes, four sites spread along 200 km of coastline were remarkably similar, sharing the same common haplotype at similar frequencies. We suggest that these four streams may have had a confluence relatively recently, possibly when sea levels were lower, 8000-10 000 BP.
Journal Article↗
Assessment of genetic structure of Greek brown hare (Lepus europaeus) populations based on variation in random amplified polymorphic DNA (RAPD).
The RAPD method was used to assess the genetic differentiation of brown hare (Lepus europaeus) populations from Central Greece. Greek wild populations were compared with samples from Austria, Poland, Germany, France, and Bulgaria, as well as with reared/released hares to investigate the impact of the releases on the native populations' genetic structure. The absence of diagnostic bands distinguishing between L. europaeus populations confirmed the high level of gene flow between brown hare populations over long geographic distances reported by other authors. Phylogenetic trees, derived from genetic distances estimated by RAPD band frequencies, suggested one major partitioning event of nuclear DNA lineages found in the samples. The reared individuals clustered with the Austrian, Polish, German, and French populations, whereas the Greek populations clustered apart with the Bulgarian population. Within Greece the distribution of the six wild populations did not follow any geographical trend, since their genetic divergence did not seem to correlate to geographic distances. However, RAPD profiles of some reared and wild specimens were different from the common RAPD pattern observed in the vast majority of sampled hares, probably reflecting an admixture of genetically differentiated individuals. The RAPD analysis indicates that releases might have begun to affect Greek population structure and reinforces the view that appropriate management is needed, adjusted to the local populations' biology and ecology.
Animals↗
Divergent operons and the genetic structure of the maltose B region in Escherichia coli K12.
Complementation and polarity suppression data are interpreted in terms of the genetic structure of the maltose B region. It is proposed that this region comprises two divergent operons. One operon includes malK, a cistron involved in maltose permeation, and lamB the only known cistron specifically involved in lambda receptor synthesis. The other operon includes malJ(1) and malJ(2) which are most probably two different cistrons, both involved in maltose permeation*. It is further assumed that expression of the two operons is controlled by malT, the positive regulatory gene of the maltose system, located in the malA region. The target(s) for the action of the malT product is (are) most likely to be located between malJ(1) and malK. There is an indication that the two operons might overlap in the region of their promoters. The structure of such an overlap as well as the possible function of the products of the different cistrons in malB are briefly discussed.
Chromosome Mapping↗
A spatial genetic structure and effects of relatedness on mate choice in a wild bird population.
Inbreeding depression, as commonly found in natural populations, should favour the evolution of inbreeding avoidance mechanisms. If natal dispersal, the first and probably most effective mechanism, does not lead to a complete separation of males and females from a common origin, a small-scale genetic population structure may result and other mechanisms to avoid inbreeding may exist. We studied the genetic population structure and individual mating patterns in blue tits (Parus caeruleus). The population showed a local genetic structure in two out of four years: genetic relatedness between individuals (estimated from microsatellite markers) decreased with distance. This pattern was mainly caused by immigrants to the study area; these, if paired with fellow immigrants, were more related than expected by chance. Since blue tits did not avoid inbreeding with their social partner, we examined if individuals preferred less related partners at later stages of the mate choice process. We found no evidence that females or males avoided inbreeding through extra-pair copulations or through mate desertion and postbreeding dispersal. Although the small-scale genetic population structure suggests that blue tits could use a simple rule of thumb to select less related mates, females did not generally prefer more distantly breeding extra-pair partners. However, the proportion of young fathered by an extra-pair male in mixed paternity broods depended on the genetic relatedness with the female. This suggests that there is a fertilization bias towards less related copulation partners and that blue tits are able to reduce the costs of inbreeding through a postcopulatory process.
Animals↗
Microsatellite and mitochondrial DNA analyses of the genetic structure of blacktip shark (Carcharhinus limbatus) nurseries in the northwestern Atlantic, Gulf of Mexico, and Caribbean Sea.
Abstract We investigated the genetic structure of blacktip shark (Carcharhinus limbatus) continental nurseries in the northwestern Atlantic Ocean, Gulf of Mexico, and Caribbean Sea using mitochondrial DNA control region sequences and eight nuclear microsatellite loci scored in neonate and young-of-the-year sharks. Significant structure was detected with both markers among nine nurseries (mitochondrial PhiST = 0.350, P < 0.001; nuclear PhiST = 0.007, P < 0.001) and sharks from the northwestern Atlantic, eastern Gulf of Mexico, western Gulf of Mexico, northern Yucatan, and Belize possessed significantly different mitochondrial DNA haplotype frequencies. Microsatellite differentiation was limited to comparisons involving northern Yucatan and Belize sharks with nuclear genetic homogeneity throughout the eastern Gulf of Mexico, western Gulf of Mexico, and northwestern Atlantic. Differences in the magnitude of maternal vs. biparental genetic differentiation support female philopatry to northwestern Atlantic, Gulf of Mexico, and Caribbean Sea natal nursery regions with higher levels of male-mediated gene flow. Philopatry has produced multiple reproductive stocks of this commercially important shark species throughout the range of this study.
Animals↗
[The phenotypic and genetic structure of the Ukrainian Grey breed of cattle].
A comparative analysis of phenotypical characteristics, the polymorphism of erythrocyte antigens and genetic-biochemical systems in the groups of Ukrainian Grey cattle, bred in Ukraine and Russia was carried out in different years. Data have been obtained on peculiarities of genetic structure of Ukrainian Grey cattle and on certain breed distinctions in the space and time.
Animals↗
The genetic structure of a province as revealed by surnames and HLA genes: potential utility in transplantation policy.
The combined use of surnames, which simulate selectively neutral genetic markers, and HLA genes may constitute a useful tool for the genetic survey of a small area. We found a coincidence between HLA genetic structure and surname "selectively neutral' pattern, in an Italian province, although HLA genes indicate a more pronounced genetic isolation for one particular subregion of the province. The patchiness of HLA allele distribution that is sometimes created by drift and/or selection can be used as the basis both of anthropological and of epidemiological studies. The creation of genetic maps of relatively small areas may also constitute a tool for the selection of bone marrow donors.
Cluster Analysis↗
Genetic structure of sylvatic, peridomestic and domestic populations of Triatoma dimidiata (Hemiptera: Reduviidae) from an endemic zone of Boyaca, Colombia.
Randomly amplified polymorphic DNA (RAPD) technique was used to study the genetic structure of sylvatic, peridomestic and domestic populations of Triatoma dimidiata. The genetic flow among them was calculated to establish the epidemiological risk of non-domiciliated populations in the transmission of Chagas disease in an endemic area of Boyaca, Colombia. A total of 83 adult specimens were studied: 26 sylvatic, 27 peridomestic and 30 domestic insects. Wright's Fst was 0.071 and the effective migration rate (Nm) 3.3, suggestive of low genetic differentiation and a movement of at least three insects per generation. The calculated percentage of polymorphic loci was 99%, confirming a large average heterozygosity due to a permanent contact between insects of the three populations. These results imply that non-domiciliated populations of T. dimidiata represent an epidemiological risk in the transmission of Chagas disease owing to the fact that they can colonize human dwellings. Close surveillance of non-strictly domiciliated species of triatomines such as T. dimidiata should entail not only the domicile but also the peridomicile and should include control programs of animal reservoirs. Houses enhancement, educational programs, surveillance of reinfestation and of individuals at risk of infection should be priorities in the control policies in endemic regions such as Boavita, Boyaca.
Animals↗
[Biochemical polymorphic systems in the immigrant population of northeastern USSR. V. Dynamics of genetic structure in individuals with different pathological processes depending upon the duration of living under extreme conditions].
It is shown that specificity of the genetic structure in individuals with different pathologic processes is interrelated to the duration of life under the extreme conditions, and its "dynamics" is contrary to that of healthy inhabitants of the region. The extent of genetic differences between groups in man and woman samples, and also between men and women in groups does not depend on the extent of differences between these groups in frequency of nosologic forms. The latter indicate that the genotype shows nonspecific disease resistance on the whole, but not to the given pathologic process. The prevalence of the average real heterozygosity over the theoretical one in sick men and the reverse effect in healthy men points to formation of new heterozygosity optimum in the extreme conditions, leading to decline in the population genetic diversity, which rather corresponds to the specific ecology. The comparison of groups of sick and healthy individuals of different life duration in the North shows that the specific weight of genotype nonspecific resistance to diseases depends mostly on the duration of life of individuals under extreme conditions, this dependence being not linear.
Adaptation, Physiological↗
Weak genetic structure indicates strong dispersal limits: a tale of two coral reef fish.
The extent of dispersal by pelagic larvae in marine environments, including coral reefs, is central for understanding local population dynamics and designing sustainable marine reserves. We present here the first example of a clear stepping-stone genetic structure throughout the Caribbean basin for a common coral reef species, the French grunt (Haemulon flavolineatum). Analysis of microsatellite DNA markers indicated that French grunt population structure may be characterized by overlapping populations throughout the Caribbean, influenced by independent population dynamics but with no fixed geographical boundaries. In addition, different spatial genetic patterns were found in different oceanographic regions. A second species, the bluehead wrasse (Thalassoma bifasciatum), has a much longer pelagic larval duration than French grunts and showed no explicit spatial pattern of genetic variation. This finding is concordant with the hypothesis of a positive relationship between larval dispersal and duration in the plankton. While the magnitude of the genetic signal of population structure in French grunts was very low (F(ST) approximately 0.003), the pattern of isolation-by-distance throughout the Caribbean indicated considerable population structure with important ecological and conservation significance.
Animal Migration↗
[Genetic structure of the populations of native inhabitants in the northeastern USSR. III. Asiatic Eskimos and the coast and reindeer Chukchi].
The genetic structure of three Asiatic eskimos subpopulations (402 individuals), five coast chuckchies subpopulations (1793 individuals) and three reindeer chuckchies subpopulations (559 individuals) have been studied for 26 electrophoretic protein systems (33 loci). These are: adenilate-kinase (AK), diaphorase NAD X H (Dia), glyoxalase-1 (GLO-1), glucose-6-phosphate dehydrogenase (6GPT), glutamatpyruvate transaminase (GPT), glutamicoxalate transaminase (GOT), carbonic anhydrase-1 (Ca-1), catalase (Ct), acid phosphatase (AcP), lactate dehydrogenase (loci LDH-A and LDH-B), leucine aminopeptidase (Lap), malatedehydrogenase (MDH), purine nucleoside phosphorylase (PNP), superoxide dismutase (Sod), 6-phosphogluconate dehydrogenase (PGD), phosphoglucomutase (loci PGM1 and PGM2), cholinesterase (loci c1--c5), alkaline phosphatase (Pp), esterase D (EsD), red cell esterase (Est) - 4 loci, albumin (Alb), haptoglobin (Hp), hemoglobine (Hb A and B), group-specific component (Gc), transferrin (Tf), ceruloplasmin (Cp). In addition, AB0 and Rh system blood groups and phenyl thiocarbamide taste sensitivity (PTC) have been studied. 12 of 36 loci are polymorphic (33.33%), heterozygosity for all loci in eskimos, coastal and reindeer chuckchies being 0.118 +/- 0.005, 0.130 +/- 0.002 and 0.120 +/- 0.004, respectively. These estimates do not differ essentially from heterozygosity at these loci for mongoloid groups living further south. The test for interpopulation heterogeneity has permitted to estimate contribution of the loci to the differentiation of these populations. The least heterogeneity has been found at loci where gene frequency distribution is the most specific for these ethnic groups.
ABO Blood-Group System↗
Integration of bacteriophages lambda and phi 80 in wild-type Escherichia coli at secondary attachment sites. II. Genetic structure and mechanism of polylysogen formation for lambda, phi 80 and the lambda att80 hybrid.
The frequency of occurrence and the genetic structure of polylysogens were studied for phages lambda, phi 80 and lambda att80. In the case of lambda, frequency of polylysogenization is high (0.20 to 0.41) with a tandem integration of prophages at the primary att site (att lambda). With phi 80 and lambda att80, this frequency is about 10 times lower, and usually one prophage becomes integrated at the primary att site (att80-I) while another (sometimes two others) integrates at one of the secondary sites. At least four secondary att80 sites have been found in wild-type Escherichia coli, two of which (near the his and tolC loci) are preferred. The frequency of secondary integration of phi 80 and lambda att80 does not differ significantly in the wild-type host and in that deleted for the primary att site (0.041 and 0.045, respectively, among surviving cells at an MOI of 10). Homoimmune superinfection has revealed a constitutive cI-independent expression of the phi 80 int gene in the prophage state. The only phi 80 tandem detected proved to be unstable. With the phi 80int- mutant, we observed stabilization of phi 80 tandems; as a consequence, their frequency of occurrence during coinfection with phi 80int+ was up to the lambda level and no nontandem insertions were found. A model is proposed for the phi 80 and lambda att80 nontandem integration.
Bacteriophage lambda↗
Selection of a suitable strain from recombinant Escherichia coli strains with the same genetic structure expressing periplasmic hGM-CSF.
The selection of a suitable strain among five recombinant Escherichia coli strains with the same genetic structure that expresses the human granulocyte macrophage colony stimulating factor (hGM-CSF) was carried out based on four criteria:growth rate, expression level, plasmid stability and feasibility for protein extraction. There was no significant difference in growth between the five strains, while a suitable expression level, a high plasmid stability and a good feasibility for protein extraction from periplasmic space were observed for one of the recombinant strains. This strain expressed 27% hGM-CSF relative to total proteins and had 96% plasmid stability after 7-d subcultures on an antibiotic-free LB medium.
Journal Article↗
Population genetic structure of the dengue mosquito Aedes aegypti in Venezuela.
The mosquito Aedes aegypti is the main vector of dengue in Venezuela. The genetic structure of this vector was investigated in 24 samples collected from eight geographic regions separated by up to 1160 km. We examined the distribution of a 359-basepair region of the NADH dehydrogenase subunit 4 mitochondrial gene among 1144 Ae. aegypti from eight collections. This gene was amplified by the polymerase chain reaction and tested for variation using single strand conformation polymorphism analysis. Seven haplotypes were detected throughout Venezuela and these were sorted into two clades. Significant differentiation was detected among collections and these were genetically isolated by distance.
Aedes↗