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At least 883 records · Page 49Linked to original sources
PubMed1993

'Inside-out', back-to-front: a model for clinical population genetic screening.

Developments in DNA technology have resulted in a dramatic increase in the number of genes identified. With the localisation of a gene it is possible to devise procedures suitable for mass carrier screening programmes. Until recently mass carrier screening was only possible for a limited number of disorders, for example, Tay-Sachs disease and haemoglobinopathies. Counselling possible carriers was based on estimations of risk. The momentum towards mass carrier screening is likely to be increased by gene therapy. Carrier screening for cystic fibrosis alone will have dramatic implications for genetic service provision as 4 to 5% of the UK population carry the CF gene. The potential for genetic screening of multifactorial diseases, for example, cancers, should also be considered. The existing organisation of genetic services is likely to be inadequate. A new specialty of clinical population genetics is required. A model is proposed of clinical population genetic screening programmes, organised under a 'common umbrella' led by a public health physician, while screening and follow up will remain the responsibility of the appropriate clinician.

Female↗
PubMed2001

Population genetic analysis of the Plasmodium falciparum erythrocyte binding antigen-175 (eba-175) gene.

The Plasmodium falciparum erythrocyte binding antigen-175 gene (eba-175) has highly divergent allelic segments (Cseg and Fseg) in one part of the gene (region III), but only a small number of single nucleotide polymorphisms (SNPs) in the rest of the sequence. Here, evidence for the possible importance of the Cseg/Fseg dimorphism was sought in a molecular population genetic analysis of the gene. First, allele frequency distributions were determined for the Cseg/Fseg dimorphism and five SNPs in a sample of five populations in Africa. The inter-population variance in frequencies was higher for Cseg/Fseg (F(ST)=0.18) than for the SNPs (F(ST) values from 0.03 to 0.10), but these values were entirely dependent on the inclusion of one particularly divergent population (Sudan). Second, linkage disequilibrium was measured among the intragenic loci. There was the expected trend of declining linkage disequilibrium with increasing molecular distance, but it is notable that the Cseg allele was in absolute linkage disequilibrium with the two flanking SNPs, whereas the Fseg allele was associated with a broader range of SNP haplotypes. Finally, there was no association between the Cseg/Fseg alleles of eba-175 in parasites and the M/N alleles of the glycophorin A erythrocyte receptor in the human subjects.

Africa↗
PubMed2001

Molecular epidemiology and population genetics in Leishmania.

Polymorphic DNA sequences have been amplified using different PCR-based techniques and used for species identification, strain discrimination and population genetic studies in Leishmania. A PCR fingerprinting method that uses single non-specific primers generates species-specific banding patterns with some intraspecies variation. This approach can be used to identify Leishmania species and also to discriminate strains of different Leishmania species. Cultivation of the parasites is, however, mandatory. PCR-restriction fragment length polymorphism of the internal transcribed spacer (ITS) in the ribosomal operon differentiates all Leishmania species, except members of the L. donovani and L. brasiliensis complexes. ITS-single-strand conformation polymorphism or ITS sequencing can detect strain specific-variation (except in L. infantum); culturing is not required. Species of Leishmania exhibit different degrees of genetic variation (L. tropica > L. aethiopica > L. major > L. donovani). Population analysis using co-dominant DNA markers developed by sequence-confirmed amplified region analysis revealed a primarily clonal structure in a L. donovani population from Sudan and suggested that occasional recombination events may occur in this population.

Animals↗
PubMed1992

[Population genetic Hae III/RFLP and HLA-DQ-alpha data of a Caucasian population sample in Switzerland].

DNA from unrelated individuals (Caucasians; n = 200-271) from Switzerland were digested with Hae III and successively hybridized to the DNA probes D1S7, D2S44, D4S139, D10S28, D14S13, D17S26 and D17S79. An allele frequency distribution was determined for each locus. Furthermore, from the same individuals (n = 200) after amplification of DNA the allele and genotype frequencies at the HLA-DQ alpha locus were determined. The allele frequency distribution in Swiss Caucasians is statistically similar to American Caucasian population samples. In criminal cases a DNA-profile derived from four single-locus probes always leads to a very high value of discrimination and in paternity testing the probability of paternity always exceeds 99.9% regardless to the reference population used for biostatistical evaluation. Therefore for use in forensic analysis and paternity testing pooled caucasian databases might be used for the determination of the frequency of occurrence of a DNA-profile.

Alleles↗
PubMed1991

[Uncovering the features of population genetic structures by the descriptive method of "genetic landscape"].

It was found that using surnames as genetical markers in rural Russian populations gives adequate results under conditions of working on the area not extending over the territory of 2 or 3 adjacent regions. Schematic drawings of genetic landscapes in 4 regions of the Kirov district and in 2 regions of the Adyg district are presented. Analysis of anomalous features of equidistant lines has been performed.

Genetics, Population↗
PubMed2002

Use of population genetic data to infer oviposition behaviour: species-specific patterns in four oak gallwasps (Hymenoptera: Cynipidae).

Many species of oak gallwasp (Hymenoptera: Cynipidae: Cynipini) induce galls containing more than one larva (multilocular galls) on their host plant. To date, it has remained unclear whether multilocular galls result solely from clustered oviposition by a single female, or include the aggregated offspring of several females (multiple founding). We have developed a novel maximum-likelihood approach for use with population genetic data that estimates the number and genotypes of parents contributing to offspring from each gall. We apply this method to allozyme data from multiple populations of four oak gallwasps whose asexual generations develop in multilocular galls (Andricus coriarius, A. lucidus, A. panteli and A. seckendorffi). We find strong evidence for multiple founding in all four species, and show the data to be compatible with multiple founding rather than founding by a single foundress mated with multiple males. The extent of multiple founding differs among species: in A. lucidus and A. seckendorffi most galls are induced by a single female, whereas in A. coriarius and A. panteli over half of the galls sampled were multiple founded. We suggest that variation in levels of multiple founding may be due to consistent ecological differences between the four species.

Adaptation, Physiological↗
PubMed1992

Sample size requirements for addressing the population genetic issues of forensic use of DNA typing.

DNA typing offers a unique opportunity to identify individuals for medical and forensic purposes. Probabilistic inference regarding the chance occurrence of a match between the DNA type of an evidentiary sample and that of an accused suspect, however, requires reliable estimation of genotype and allele frequencies in the population. Although population-based data on DNA typing at several hypervariable loci are being accumulated at various laboratories, a rigorous treatment of the sample size needed for such purposes has not been made from population genetic considerations. It is shown here that the loci that are potentially most useful for forensic identification of individuals have the intrinsic property that they involve a large number of segregating alleles, and a great majority of these alleles are rare. As a consequence, because of the large number of possible genotypes at the hypervariable loci that offer the maximum potential for individualization, the sample size needed to observe all possible genotypes in a sample is large. In fact, the size is so large that even if such a huge number of individuals could be sampled, it could not be guaranteed that such a sample was drawn from a single homogeneous population. Therefore adequate estimation of genotypic probabilities must be based on allele frequencies, and the sample size needed to represent all possible alleles is far more reasonable. Further economization of sample size is possible if one wants to have representation of only the frequent alleles in the sample, so that the rare allele frequencies can be approximated by an upper bound for forensic applications.

Alleles↗
PubMed2006

Natal philopatry does not lead to population genetic differentiation in Buller's albatross (Thalassarche bulleri bulleri).

Genetic variability in the only two existing populations of Buller's albatross (Thalassarche bulleri bulleri) was assessed using six polymorphic microsatellite loci. Large biological samples were obtained from both the Snares (n = 99) and the Solander Islands (n = 27). Several measures of genetic differentiation including F(ST) and R(ST) and a principal coordinates analysis (PCO) suggest a complete absence of genetic structure between three breeding colonies on the Snares Islands, and between them and one breeding colony on the Solander Islands. Mark/recapture studies of recently banded albatross chicks on the Snares found high natal philopatry in T. b. bulleri, but the microsatellite DNA data suggest that sufficient gene flow still occurs between all four breeding colonies to maintain a genetically homogeneous population overall.

Animals↗
PubMed2026

Sugar kelp (Saccharina latissima) population genetics map onto geographic distance and oceanographic features across coastal Maine.

Sugar kelp (Saccharina latissima; order Laminariales) plays a vital role in kelp forest ecosystems, as well as an expanding kelp aquaculture industry, in the Gulf of Maine, United States. However, ocean warming is eroding the resilience of Maine's kelp forests and may be compromising their local genetic diversity, with impacts on population structure and gene flow. Here, we used genome-wide single nucleotide polymorphism (SNP) data to assess the genetic diversity, structure, and connectivity of S. latissima populations at 11 outer coastal sites spanning the historical range of kelp forests in Maine. Our analyses identified moderate genetic diversity and limited inbreeding within sites (average heterozygosity: 0.27). Further, they revealed that three clusters comprising four genetically distinct populations exist across the study region. Population structure was strongly associated with geographic distance and oceanographic features, as supported by principal coordinate analysis, FST calculations, Bayesian clustering, and spore dispersal modeling. Lastly, our outlier analysis identified genes potentially under selection. Thus, our findings highlight distinct, genetically unique kelp populations along Maine's coast and emphasize the need for regional management strategies that support both ecosystem resilience and sustainable aquaculture under climate change.

Gulf of Maine↗
PubMed2006

Population genetics of Ochlerotatus eatoni (Diptera: Culicidae) endemic species to two Macaronesian Islands.

Analyses of 11 isoenzyme loci of Ochlerotatus eatoni (Edwards, 1916), endemic to two Macaronesian Islands (Madeira and Tenerife, Canary Islands), revealed substantial genetic structure in the study populations. Samples from sites on the south and north of Madeira displayed a significant reduction of variability compared with those from central Madeira and Tenerife. The Tenerife population exhibited a severe deficit of heterozygosity with similar magnitude across all the loci examined. The complex pattern of variation in Oc. eatoni is because of interplay of breeding structure, genetic drift, and geographical and historical factors. From these findings, we concluded that island colonization by Oc. eatoni was not marked by founder effect.

Animals↗
PubMed1989

Genetic studies of low-abundance human plasma proteins. XIII. Population genetics of C1R complement subcomponent and description of new variants.

Isoelectric focusing and immunoblotting reveals considerable biochemical and genetic variation in the C1R subcomponent of the first complement component. The nature of the intraindividual biochemical variation can be explained by differences in sialic acid content because after digestion with neuraminidase the terminal sialic acids are removed to yield a single major band corresponding to the C1R polypeptide. Plasma samples from a large number of different ethnic groups, consisting of U.S. whites, U.S. blacks, Nigerian blacks, and Inuit, Aleut, and Amerindian populations from the Western Hemisphere have revealed genetically determined charge variation with heterozygous phenotypes consisting of two major asialo bands, indicating that the underlying variation is not due to variation in sialic acid content. Two previously reported common alleles, C1R*1 and CIR*2, have been observed in all studied populations, the notable exception being the Dogrib Indian population, which is devoid of the C1R*2 allele. Several new alleles--designated C1R*3, C1R*4, C1R*5, C1R*6, and C1R*7-have been observed, with variable frequencies ranging from the occurrence in a single individual and related family members to the polymorphic occurrence of certain alleles in several populations. Of these new alleles, the C1R*5 is of considerable interest in population and anthropological genetics studies. The C1R*5 allele is widely distributed, at a frequency of .03 to .17, in all of the North American aboriginal populations screened. This allele is not present in U.S. whites but is present at a polymorphic frequency in U.S. and Nigerian blacks.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed2003

Tsetse fly population genetics: an indirect approach to dispersal.

Tsetse populations are distributed discontinuously, particularly the morsitans group. Dispersal among diverse populations cannot easily be measured directly because the geographical distances between them can be too great to have a reasonable expectation of recapturing experimentally released flies. Moreover, reproductive success of widely dispersed flies might be poor. The question of dispersal rates in tsetse is immediately important because area-wide eradication plans involving the sterile insect technique are under consideration. Dispersal and gene flow are important from evolutionary and historical viewpoints. An indirect method of estimating dispersal is to measure gene flow. Genetic data indicate surprisingly low rates of gene flow in the morsitans and palpalis groups studied to date. The underlying assumptions in making such estimates need to be examined carefully, however, before accepting firm conclusions, and further research is needed. Of particular interest is the question of tsetse adaptation to local environments.

Animals↗
PubMed2002

Investigation of the population genetic structure and mating system in the ant Pheidole pallidula.

The origin of eusociality in haplo-diploid organisms such as Hymenoptera has been mostly explained by kin selection. However, several studies have uncovered decreased relatedness values within colonies, resulting primarily from multiple queen matings (polyandry) and/or from the presence of more than one functional queen (polygyny). Here, we report on the use of microsatellite data for the investigation of sociogenetic parameters, such as relatedness, and levels of polygyny and polyandry, in the ant Pheidole pallidula. We demonstrate, through analysis of mother-offspring combinations and the use of direct sperm typing, that each queen is inseminated by a single male. The inbreeding coefficient within colonies and the levels of relatedness between the queens and their mate are not significantly different from zero, indicating that matings occur between unrelated individuals. Analyses of worker genotypes demonstrate that 38% of the colonies are polygynous with 2-4 functional queens, and suggest the existence of reproductive skew, i.e. unequal respective contribution of queens to reproduction. Finally, our analyses indicate that colonies are genetically differentiated and form a population exhibiting significant isolation-by-distance, suggesting that some colonies originate through budding.

Animals↗
PubMed1992

Population genetic analysis of Borrelia burgdorferi isolates by multilocus enzyme electrophoresis.

Fifty Borellia burgdorferi strains isolated from humans and ticks in Europe and the United States were analyzed by multilocus enzyme electrophoresis. Eleven genetic loci were characterized on the basis of the electrophoretic mobilities of their products. Ten loci were polymorphic. The average number of alleles per locus was 5.9, with a mean genetic diversity of 0.673 among electrophoretic types (ETs). The strains were grouped into 35 ETs constituting three main divisions (I, II, and III) separated at a genetic distance greater than 0.75. Divisions I, II, and III contained 13, 6, and 16 ETs, respectively. These findings, together with previous data from DNA hybridization and restriction enzyme analysis of rRNA genes, suggest that divisions I, II, and III may represent three distinct genomic species. All three divisions contained human clinical ETs. However, in division I, which includes the ET of the type strain of B. burgdorferi, the human pathogenic ETs constituted a single clone. The ETs of division I were from west-central Europe and the United States, whereas divisions II and III contained ETs from west-central and northern Europe but not from the United States. Finally, our data show that the genetic structure of B. burgdorferi populations is clonal.

Alleles↗