The founder effect and deleterious genes

During the rapid growth of a population from a few founders, a single deleterious gene in a founder can attain an appreciable frequency in later generations. A computer simulation, which has the population double itself in early generations, indicates a lethal could attain a frequency of 0.1. Since deleterious recessive genes are eliminated from large populations at a very slow rate, variations in their frequencies in present major human populations may be due to the founder effect during earlier rapid expansion.     

Volodymyr Petrovych Vendt--a founder of sceintific trends in photobiochemistry and biotechnology in Ukraine

Professor Volodymyr Petrovych Vendt (30.11.1906, Kremenchug, Ukraine-22.11.1997, Kyiv, Ukraine), Doctor of science (biol.), Laureate of the State Prize of Ukraine graduated from the Odessa Physico-Pharmaceutical Institute (1930) in speciality chemist-analyst and was assigned to work at the Ukrainian Institute of Pathology and Labour Hygiene in Kharkiv. He was soon taken on as a scientific worker at the Ukrainian Institute of Experimental Medicine. He defended his thesis for the Candidate's degree and acquired the academic status of the senior scientific worker in 1939, and that of docent (assistant professor) in 1940. In 1938-1941 Volodymyr Petrovych read lectures at the Department of Chemistry of the Academy of Service Corps of the Workers' and Peasants' Red Army. At that time his scientific interests were connected with development of simple express-methods for detecting various substances, including chemical weed- and pest-killers which were used in agriculture. In 1944-1946 V. P. Vendt took part in military operations at the 1st Ukrainian Front, and after the release he was taken on as the senior scientific worker at the Institute of Biochemistry of the Academy of Sciences of the Ukrainian SSR, where he worked during 47 years. In 1961, after defending the thesis for the Doctor's degree Volodymyr Petrovych acquired the academic status of professor. In 1963 V. P. Vendt became a head of the Laboratory and then (1966) - of the Deaprtment of Photobiochemistry and from 1976 to 1983 - the Department of Sterol Biochemistry. He was the first to make the broad-scale investigations of sterol biochemistry, first of all group D vitamins, and came close to finding out the action mechanism of vitamin D3 - cholecalciferol. V. P. Vendt was one of the first to show a possibility of formation of sterene complexes with proteins and to find out the nature of chemical relations between them. That made it possible to develop the methods of obtaining artificial protein-vitamin complexes of high activity on the basis of casein (or other proteins) with preparations of vitamins D2, D3, E, carotene. Vitamin industry of the USSR used the technology, elaborated by V. P. Vendt, for the industrial production of vitamin D3 (videin D3) for poultry farming and medicine. He offered the method of early diagnosis of D-hypovitaminosis in chickens and developed and put into medical practice the methods of early diagnosis of rachitis in children and the degree of the disease risk by the umbilical blood analysis. V. P. Vendt and R. I. Yakhymovych were the first to obtain crystalline vitamin D3 and its complex with cholesterol (videchol) which was successfully used for rachitis prophylaxis and therapy in children. V. P. Vendt is the author of above 200 scientific works, 17 author's certificates and inventions. The scientific school of V. P. Vendt numbers 4 doctors and 16 candidates of science and above 60 research workers. The selfless work of the scientist was marked by state awards--by six medals and the State Prize of Ukraine in the field of science and technology "For investigations in vitamin D chemistry and biochemistry, creation of industrial technology of its production and introduction into medicine and agriculture" (jointly with R. I. Yakhymovych).     

Investigation on the founder effect

The fitness of threeDrosophila melanogaster populations (A,B,C) and the crosses between them (A×B; A×C; B×C) has been studied in conditions of overlapping generations. Each line was subdivided into 4 sub-populations (1,2,3,4) differing in the phenotype of the founder flies (vestigial or wild type) and of which sub-populations 2 and 3 had the same gene composition. Fitness was estimated as the number of adult flies present in each population. The results suggest that: (1) a differentiation of fitness values is detectable between sub-populations founded from groups of flies having the same gene composition; (2) isolation does not seem to be a necessary condition for the observed differentiation. These results are discussed in connection with the evolutionary effects of random genetic drift. A working hypothesis has been advanced which would explain the observed results as dependent on complex interactions involving sexual dimorphism and interactions between genes.     

The effective founder effect in a spatially expanding population

The gradual loss of diversity and the establishment of clines in allele frequencies associated with range expansions are patterns observed in many species, including humans. These patterns can result from a series of founder events occurring as populations colonize previously unoccupied areas. We develop a model of an expanding population and, using a branching process approximation, show that spatial gradients reflect different amounts of genetic drift experienced by different subpopulations. We then use this model to measure the net average strength of the founder effect, and we demonstrate that the predictions from the branching process model fit simulation results well. We further show that estimates of the effective founder size are robust to potential confounding factors such as migration between subpopulations. We apply our method to data from Arabidopsis thaliana. We find that the average founder effect is approximately three times larger in the Americas than in Europe, possibly indicating that a more recent, rapid expansion occurred.     

The founder effect in a human isolate: evolutionary implications

An investigation of the founder effect has been made on the H-leut, a religious isolate. Ninety-one founders, representing a maximum of 150 independent genomes, have been shown to account for the total gene pool of the 9,536 people in two of the three major subpopulations within the isolate, the S-leut and the L-leut. Each of these two leut is subdivided into four clans which in turn are subdivided into colonies. Malécot's coefficient of kinship has been calculated between each of the 91 founders and the contemporary parents, and used to describe the relative genetic contributions of the founders to the gene pool of each subpopulation. Analysis of this distribution suggests that a considerable amount of genetic diversity may be attributable to the founder effect. Part of this diversity may be accounted for by variation in the birth dates of the founders. The size of the subset of the 91 founders related to each subpopulation decreases with decreasing subpopulation level. A correlation has been found between two measures of relationship between pairs of clans: (1) Kurczynski's modification of Mahalanobis's distance measure based on gene frequency differences; and (2) a comparison of the relative contributions of founders to the gene pools of the clans.     

The Eskimo isolate of Scoresbysund—an example of the founder effect in anthropology

The east coast of Greenland is inhabited in only two places: in Angmagssalik live the direct descendants of the 413 Eskimo discovered in 1884; 1000 km further north, a small isolated settlement, Scoresbysund, was founded in 1925 by 70 Eskimo from Angmagssalik.Several biological features were studied both on the parent population and its descendants and the founders themselves and their progeny. Moreover, detailed and periodically maintained genealogical records from the time of their discovery provide exceptional complete information on these two groups and make them particularly favourable for the study of certain anthropological and genetic problems.Regarding various hereditary anthropological characteristics (blood groups, finger patterns, anthropometric measurements), the isolate shows certain particularities compared to the parent population. There is a much greater ressemblance between the settlement's founders and their present descendants than between these two groups and the parent population and its descendants. A set of converging elements indicate that this isolate represents a good example of the founder effect for various anthropological characteristics.     

The split of the Arara population: comparison of genetic drift and founder effect

The total genetic diversity of the Amerindian population is as high as that observed for other continental human populations because a large contribution from variation among tribes makes up for the low variation within tribes. This is attributed mainly to genetic drift acting on small isolated populations. However, a small founder population with a low genetic diversity is another factor that may contribute to the low intratribal diversity. Small founder populations seem to be a frequent event in the formation of new tribes among the Amerindians, but this event is usually not well recorded. In this paper, we analyze the genetic diversity of the Arara of Laranjal village and the Arara of Iriri village, with respect to seven tandem repeat autosomic segments (D1S80, ApoB, D4S43, vW1, vW2, F13A1 and D12S67), two Y-chromosome-specific polymorphisms (DYS19 and DYS199), and mitochondrial DNA (mtDNA) markers (restriction fragment length polymorphisms and sequencing of a segment of the D loop region). The occurrence of a single Y chromosome and mtDNA haplotype, and only 1-4 alleles of the autosomic loci investigated, corroborates historic and demographic records that the Arara of Iriri were founded by a single couple of siblings who came from the Arara of Laranjal, the largest group. Notwithstanding this fact, the genetic distance and the molecular variance between the two Arara villages were greater than those observed between them and other Amazonian tribes, suggesting that the microevolutionary process among Brazilian Amerindians may be misinterpreted if historic demographic data are not considered.     

Occupational risk factors in the biotechnology industry and workers' health status]

The mechanisms of the pathogenic effect of microbial cultures used in biotechnological industry and the products of their vital activity on the workers were investigated. A unique classification of the components of the disease incidence with temporary disability is described. The necessity of detecting prepathological conditions and initial occupational affections in the workers for preventing severe consequences of occupational diseases is indicated. On the basis of complex investigations of disease incidence in the workers, revision of the present sanitary and hygienic regulations may be of need.     

Cystic fibrosis in the Ohio Amish: Gene frequency and founder effect

A high incidence of cystic fibrosis (CF), 1/569 live births (0.00176), was found among 10 816 live births in an Ohio Amish isolate. The minimum gene frequency calculated from this incidence was 0.042. In marked contrast, a second Amish isolate was described with no occurrence of CF among 4448 live births. Founder effect is the most probable explanation for the difference in the CF gene frequency between the two communities. Pedigree analysis identified a single ancestral couple born in the 1700s common to all obligate heterozygotes.     

A striking example of the founder effect in the mollusc Littorina saxatilis

Two South African populations of Littorina saxatilis were examined by starch-gel electrophoresis at 16 enzyme loci and compared with 13 populations of North Atlantic saxatilis from both American and European coasts, and with six British populations of the closely related species Littorina arcana. The South African animals showed a severely reduced heterozygosity (– 0.052) compared with Atlantic populations of saxatilis ( = 0.181), and the mean genetic distance between the two areas was high ( = 0.203) compared with distances within the North Atlantic saxatilis populations (D = 0.034). In fact, the saxatilis from South Africa were genetically more distant from the North Atlantic samples of L. saxatilis than were the arcana from British shores. The reduced genetic heterozygosity and genetic divergence of the South African populations is attributed to founder effects following a postulated recent introduction by man.     

Lafora disease and founder effect in a small neotropical locality

The Lafora disease is an uncommon genetic condition. Four cases (two families) were detected in Zarcero, a small town in Costa Rica (population under 2000). They belonged to two separate consanguineous marriages but both families had common ancestors. The diagnosis of Lafora disease was confirmed by liver biopsy in one of the patients. The ages of onset were 13, 14, 16 and 17 years. Patients died after four, nine, six and five years of severe progressive physical and mental deterioration, respectively. The gene for Lafora disease arrive to Zarcero from one of its founders. There are no other cases reported from Costa Rica: this is an example of genetic drift, or more specifically, founder effect.     

Diverging patterns of mitochondrial and nuclear DNA diversity in subarctic black spruce: imprint of a founder effect associated with postglacial colonization

High-latitude ecotonal populations at the species margins may exhibit altered patterns of genetic diversity, resulting from more or less recent founder events and from bottleneck effects in response to climate oscillations. Patterns of genetic diversity were investigated in nine populations of the conifer black spruce (Picea mariana [Mill.] BSP.) in northwestern Québec, Canada, using seed-dispersed mitochondrial (mt) DNA and nuclear (nc) DNA. mtDNA diversity (mitotypes) was assessed at three loci, and ncDNA diversity was estimated for nine expressed sequence tag polymorphism (ESTP) loci. Sampling included populations from the boreal forest and the southern and northern subzones of the subarctic forest-tundra, a fire-born ecotone. For ncDNA, populations from all three vegetation zones were highly diverse with little population differentiation (thetaN = 0.014); even the northernmost populations showed no loss of rare alleles. Patterns of mitotype diversity were strikingly different: within-population diversity and population differentiation were high for boreal forest populations [expected heterozygosity per locus (HE) = 0.58 and thetaM = 0.529], but all subarctic populations were fixed for a single mitotype (HE = 0). This lack of variation suggests a founder event caused by long-distance seed establishment during postglacial colonization, consistent with palaeoecological data. The estimated movement of seeds alone (effective number of migrants per generation, NmM < 2) was much restricted compared to that estimated from nuclear variants, which including pollen movement (NmN > 17). This could account for the conservation of a founder imprint in the mtDNA of subarctic black spruce. After reduction, presumably in the early Holocene, the diversity in ncDNA would have been replenished rapidly by pollen-mediated gene flow, and maintained subsequently through vegetative layering during the current cooler period covering the last 3000 years.     

The greening of biotechnology: the growth of the US biotechnology industry

The growth and advancement of biotechnology worldwide has been the focus of many studies, and at the heart of this advancement has been a new industry of small biotechnology firms in the United States. Since the early 1970s more than 300 small companies have been founded in the United States to work with the new technologies of genetic engineering, monoclonal antibody production, and in related areas. In addition, many major corporations in the United States have sought entry into biotechnology. Hundreds of new companies have been founded to interact with the biotechnology firms and large corporations, supplying reagents, equipment, fermentation expertise and serving a variety of other ancillary functions. Nowhere else in the world has a biotechnology industry been initiated to such a large degree. Today, the average US biotechnology firm is six to seven years old. The current state of the US biotechnology industry, historical perspectives, major trends and some future outlooks will be described below.     

The legacy effect of biochar application on soil nitrous oxide emissions

Existing studies suggest that biochar application can reduce soil nitrous oxide (N₂O) emissions, mainly based on short-term results. However, it remains unclear what the effects (i.e., legacy effects) and underlying mechanisms are on N₂O emissions after many years of a single application of biochar. Here, we collected intact soil columns from plots without and with biochar application in a subtropical tea plantation 7 years ago for an incubation experiment. We used the N₂O isotopocule analysis combined with ammonia oxidizer-specific inhibitors and molecular biology approaches to investigate how the legacy effect of biochar affected soil N₂O emissions. Results showed that the soil in the presence of biochar had lower N₂O emissions than the control albeit statistically insignificant. The legacy effect of biochar in decreasing N₂O emissions may be attributed to the reduced effectiveness of the soil substrate, nitrification and denitrification activities, and the promotion of the further reduction of N₂O. The legacy effect of biochar reduced the relative contribution of nitrifier denitrification/bacterial denitrification, nitrification-related N₂O production, and the relative abundance of several microorganisms involved in the nitrogen cycle. Our global meta-analysis also showed that the reduction of N₂O by biochar increased with increasing application rate but diminished and possibly even reversed with increasing experimental time. In conclusion, our findings suggest that the abatement capacity of biochar on soil N₂O emissions may weaken over time after biochar application, but this remains under further investigation.     

The effect of soil legacy on competition and invasion by Acacia dealbata Link

Plant–soil feedbacks can exacerbate competition between invasive and native species, although the net effect of the interaction between soil biota and competition is likely to be species-specific. Very few studies have addressed the combined effect of soil and competition on plant performance and invasion by exotic woody species. This study explores plant growth and competition between Acacia dealbata and Pinus pinaster in three different soils—native, disturbed and invaded—in Portugal. The invasion of native P. pinaster forests by A. dealbata can be explained by the stronger competition ability of the exotic tree species. Competition is stronger in the native soil, allowing the establishment of A. dealbata in this soil and the displacement of P. pinaster. During invasion, A. dealbata changes soil conditions and establishes positive plant–soil feedbacks that promote its own germination and growth and increase P. pinaster mortality. Soil disturbance by the introduction of a different exotic species, Eucalyptus globulus, did not promote invasion by A. dealbata. We found a significant effect of soil legacy on both growth and competitive ability of the invasive A. dealbata. The ability of A. dealbata to outcompete the native P. pinaster in its own soil and the positive plant–soil feedbacks established after invasion are important mechanisms for A. dealbata invasion.