Genetic distance in inversion polymorphism among natural populations of Drosophila ananassae

Based on the differences in the gene arrangement frequencies average genetic distance has been estimated among natural populations of Drosophila ananassae. Genetic distance obtained by pairwise comparison ranges from 0.002 to 0.371. The most differentiated populations are those from the Andaman and Nicobar Islands. Although the populations from localities separated by a small geographic distance show less genetic distance, the relation between genetic distance and geographic distance does not seem to be positive.     

Genetic structure and AFLP variation of remnant populations in the rare plant Pedicularis palustris (Scrophulariaceae) and its relation to population size and reproductive components

We investigated plant reproduction in relation to genetic structure, population size, and habitat quality in 13 populations of the rare biennial plant Pedicularis palustris with 3-28500 flowering individuals. We used AFLP (amplified fragment length polymorphism) profiles to analyze genetic similarities among 129 individuals (3-15 per population). In a cluster analysis of genetic similarities most individuals (67%) were arranged in population-specific clusters. Analysis of molecular variance indicated significant genetic differentiation among populations and among and within subpopulations (P < 0.001). Gene flow (N(e) m) was low (0.298). On average, plants produced 55 capsules, 17 seeds per fruit, and 42 seedlings in the following growing season. The number of seeds per capsule was independent of population size and of genetic variability. In contrast, the number of capsules per plant (P < 0.05) and the number of seedlings per plant (P < 0.05) were positively correlated with population size. The relation between population size and the number of seeds per plant was not significant (P = 0.075). The number of capsules and of seeds and seedlings per plant (P < 0.01) were positively correlated with genetic variability. Genetic variability was independent of actual population size, suggesting that historical population processes have to be taken into account, too. Stepwise multiple regressions revealed additional significant relationships of habitat parameters (soil pH, C:N ratio), vegetation composition, and standing crop on reproductive components. We conclude that populations of P. palustris are genetically isolated and that reproductive success most likely is influenced by population size, genetic variability, and habitat quality. Management strategies such as moderate grazing, mowing, and artificial gene flow should endeavor to increase population size as well as genetic variation.     

Communication of Genetic Information within Families: The Case for Familial Comity

Advances in genetic technologies raise a multitude of ethical issues, some of which give rise to novel dilemmas for medical practice. One of the most controversial problems arising in clinical genetics is that of confidentiality and who may disclose genetic health information. This paper considers the question of when it is appropriate for health professionals to disclose clinically significant genetic information without patient consent. Existing ethical principles offer little guidance in relation to this issue. We build on suggestions that genetic information may be viewed as collective or shared information, and we introduce the concept of ‘familial comity’ as a fresh way to consider the issues.Competing Interests: None declared. Funding: No special funding was secured for this research.     

Genetic-geographic dispersion among North Indian populations and affinities of the Jats

Variation in 13 loci across North India has been mapped using principal components and generalized distance analysis. Significant clinal variation is documented for most systems, and genetic difference bears a relation to geographic distance especially along a north-west-to-southeast inclination. Both caste and geography exert influence over the historically contentious affinities of the Jats. Author order is alphabetical     

Between nurture and nature: the shifting determinants of female fertility in Danish twin cohorts

Behaviors related to fertility constitute primary candidates for investigating the relevance of evolutionary influences and biological dispositions on contemporary human behaviors. Using female Danish twin cohorts born 1870-1968, we document important transformations in the relative contributions of "nurture" and "nature" to within-cohort variations in early and complete fertility, and we point toward a systematic relation between the socioeconomic context of cohorts and the relevance of genetic and shared environmental factors. This transformation is most striking for early fertility where genetic factors strengthen over time and are consistent with up to 50 percent of the variation in early fertility in most recent cohorts. Understanding this emerging relevance of genetic factors is of central importance because early fertility constitutes an important determinant of complete fertility levels in low-fertility societies, and because teenage motherhood and early childbearing are often associated with negative life-cycle consequences. Moreover, our results emphasize the need for socially and contextually informed analyses of nature and nurture that allow both factors to influence human reproductive behavior over time.     

Owning Genetic Information and Gene Enhancement Techniques: Why Privacy and Property Rights May Undermine Social Control of the Human Genome

In this article I argue that the proper subjects of intangible property claims include medical records, genetic profiles, and gene enhancement techniques. Coupled with a right to privacy these intangible property rights allow individuals a zone of control that will, in most cases, justifiably exclude governmental or societal invasions into private domains. I argue that the threshold for overriding privacy rights and intangible property rights is higher, in relation to genetic enhancement techniques and sensitive personal information, than is commonly suggested. Once the bar is raised, so-to-speak, the burden of overriding it is formidable. Thus many policy decisions that have been recently proposed or enacted – citywide audio and video surveillance, law enforcement DNA sweeps, genetic profiling, national bans on genetic testing and enhancement of humans, to name a few – will have to be backed by very strong arguments.     

Distribution of genetic diversity within and between Western Mediterranean island populations of the black rat Rattus rattus (L. 1758)

Genetic diversity was estimated by allozyme analysis at 26 loci in black rat populations (Rattus rattus) from 15 western Mediterranean islands (Hyéres, Corsica, Sardinia and related islets). Although overall variability levels were low (H = 0.025), the mean heterozygosity values for the islands were similar to those for three reference mainland populations. Within the islands, however, genetic diversity varied in relation to island size and geographic isolation. In particular, most small insular populations were significantly more variable than those on both large and isolated islands. The generic relationships between island populations were established by F_ST analyses indicating possible geographic origins and patterns of colonization. The maintenance of unexpectedly high levels of variability in the small island populations is discussed in relation to changes in the demographic and social structure observed in these populations. These island populations of black rat illustrate how genetic diversity may be efficiently maintained in a series of interconnected spatially fragmented populations.     

Genetic Identity of Populus tremuloides Litter Influences Decomposition and Nutrient Release in a Mixed Forest Stand

Recent research has shown that genetic variation can directly impact community and ecosystem level processes. Populus tremuloides (trembling aspen) is an extremely widespread and genetically diverse tree species important to many North American forest ecosystems. Using leaf litter from five genotypes grown in a common garden under two nutrient treatments, we tracked litter decomposition in a natural aspen stand for 1 year. Here we show that aspen leaf litter decomposes and releases carbon, nitrogen, and sulfur in relation to its genetic identity. In a secondary experiment, we show that the genetic diversity of aspen litter mixtures can influence decomposition, however weakly so. Overall, nutrient treatments influenced leaf litter decomposition the most, followed by genetic identity, and then by genetic diversity (if at all in some cases). In this widespread, genetically diverse, and dominant species, genetic variation within a single species is important to ecosystem functioning. The relatively weak effect of genetic diversity on the processes measured here does not preclude its importance to ecosystem functioning, but does suggest that genetic identity and composition are more important than genetic diversity per se.     

三个不同海拔梯度马尾松种群的遗传多样性及其与生态因子的相关性

采用RAPD技术分析测定了3个马尾松海拔梯度种群的分子遗传 征。马尾松种群中遗传多样性较高,AMOVA软件分析Euclidean系数SSD总和达8164.116;L1、L2、L3三个种群的遗传多样性分别为7.4832、7.4011、7.0332。种群间的分化程度较低,大部分变异存在于种群内（约≥97％）,种群间仅占一小部分（约≤2％）;相关性分析表明种群的遗传多样性与土壤的总氮量呈显著负相关性（P＜0.05）,而与其它生态因子相关关系不显著;虽然种群间遗传距离值均很低（L1－L2、L2－L3、L1－L3分别为－0.0002、0.0001、0.0051）,但其值与海拔差距呈显著正相关性。     

Panicum spikelets from the Early Holocene Takarkori rockshelter (SW Libya): Archaeo-molecular and -botanical investigations

This paper deals with the extraction, amplification and sequencing of ancient DNA (aDNA) from spikelets of wild cereals dated at ca. 9000 cal yr BP, representing the most ancient plants with preserved genetic material from the Sahara desert. The sub-fossil records were collected from the archaeological excavation carried out at Takarkori, an archaeological site located in south-western Libya. Morphological and genetic analyses were made on 100 well preserved dried spikelets. Ten DNA extraction protocols were performed to evaluate nucleic acid recovery in terms of DNA yield, purity and amplification success of the chloroplast barcode region matK. The extraction protocol that returned the most suitable DNA to be amplified is the Kistler and Shapiro (2011: J Archaeol Sci 38: 3549-3554) modified protocol. In our study, the results from matK amplification suggested that four specimens are the most appropriate number of spikelets for these analyses. DNA was then used for PCR amplifications of four chloroplast barcode genes: rbcL, matK, trnH-psbA and trnL. A phylogenetic analysis shows the strict relation between the archaeological specimens and modern Panicoideae, supporting the morphological identification. The results indicate that spikelets have a close relation to Panicum laetum Kunth, a wild cereal still collected in tropical Africa.     

Genetic resource impacts of habitat loss and degradation; reconciling empirical evidence and predicted theory for neotropical trees

The theoretical impacts of anthropogenic habitat degradation on genetic resources have been well articulated. Here we use a simulation approach to assess the magnitude of expected genetic change, and review 31 studies of 23 neotropical tree species to assess whether empirical case studies conform to theory. Major differences in the sensitivity of measures to detect the genetic health of degraded populations were obvious. Most studies employing genetic diversity (nine out of 13) found no significant consequences, yet most that assessed progeny inbreeding (six out of eight), reproductive output (seven out of 10) and fitness (all six) highlighted significant impacts. These observations are in line with theory, where inbreeding is observed immediately following impact, but genetic diversity is lost slowly over subsequent generations, which for trees may take decades. Studies also highlight the ecological, not just genetic, consequences of habitat degradation that can cause reduced seed set and progeny fitness. Unexpectedly, two studies examining pollen flow using paternity analysis highlight an extensive network of gene flow at smaller spatial scales (less than 10 km). Gene flow can thus mitigate against loss of genetic diversity and assist in long-term population viability, even in degraded landscapes. Unfortunately, the surveyed studies were too few and heterogeneous to examine concepts of population size thresholds and genetic resilience in relation to life history. Future suggested research priorities include undertaking integrated studies on a range of species in the same landscapes; better documentation of the extent and duration of impact; and most importantly, combining neutral marker, pollination dynamics, ecological consequences, and progeny fitness assessment within single studies.     

Genetic diversity of Tibraca limbativentris Stål (Hemiptera: Pentatomidae) of Santa Catarina and Rio Grande do Sul, Brazil, using RAPD

The work was carried out to test DNA extraction protocols and to characterize populations of Tibraca limbativentris St?l, an important rice insect-pest. Insects were collected in Joinville, Rio do Oeste and Turvo, in Santa Catarina State, and Agudo, Uruguaiana, Pelotas and Palmares do Sul, in Rio Grande do Sul State, and six literature-referenced protocols, besides a new one, were tested. DNA from ten individuals of each population was extracted using the best protocol and RAPD reactions were carried out with ten initiators. The new protocol showed the best results and was used in the PCR reactions, that generated 151 polymorphic bands, allowing to access genetic differences among all the populations; no individuals from one population were clustered with individuals from another. The largest intrapopulacional similarity was found in Uruguaiana (22%), and the smallest in Palmares do Sul (50%), which was also the most divergent population in relation to the others. The Gst was 0.5215, and the Nm was 0.4588; these values reflect the low similarity between the populations. The smallest genic flow was obtained when Palmares do Sul and Pelotas were included in the comparisons, in accordance with the largest divergence of these two populations in relation to the others. There was no significant relation between geographic distance and genetic similarity, which can reflect unknown model of dispersion of T. limbativentris. New studies exploring the species dispersion strategies may help to understand the insect distribution and to unveil the main factors linked to the genetic variability within and between populations.     

Genetic and physiological studies of bacteriophage t5 I. An expanded genetic map of t5

An expanded genetic map of bacteriophage T5 has been constructed by using a set of amber, rather than temperature-sensitive, mutants that represent 29 cistrons. The map consists of three small groups and one large group of genes; mutants defective in genes that are located in different groups exhibit maximal recombination when crossed with one another. However, it has been possible to establish tentative linkage among these groups by use of a particular mutant that appears to affect recombination. One of the small groups of genes is located in the first-step-transfer or FST segment; the other two small groups represent newly discovered genetic regions. The large group probably includes most or all of the previously published maps of T5. The apparent genetic discontinuities are discussed in relation to certain anatomical and physiological features that are unique to bacteriophage T5.     

Genetic counseling and the caudal regression syndrome

It has been published about 500 cases of caudal regression (sacral agenesis) of which 12 are undoubtly familial. In most of the non familial cases an aetiology is not demonstrable except the cases related to maternal diabetes and/or insulin treatment. A genetic control of the caudal regression is implicit in the familial transmission. Three sporadic new cases are reported and, at the occasion of the genetic counselling we analyse the 8 well reported genealogies. Among 133 subjects, 72 show some evidences of caudal regression. This is compatible with a pattern of autosomic dominant transmission. The analogy with the caudal regression anomaly of the mouse, in which the role of genes located closely to the histocompatibility system is demonstrated, evokes such a relation in the human with the major histocompatibility system. If true, this may be used as a genetic marker, especially for early antenatal diagnosis.     

吉林爆玉米遗传距离与杂种优势关系的研究

根据吉林省80个爆玉米自交系数量性状的表现,估算了它们之间的遗传距离。又估算了这80个自交系间随机组配的67个杂交组合F1代小区产量、爆粒率和膨胀倍数的杂种优势。相关和回归分析表明,F1代产量的对照优势与其双亲之间的遗传距离呈显著的二次曲线关系,而F1代品质特性爆粒率和膨胀倍数的对照优势与其双亲之间的遗传距离无确定性关系。因此,可以根据亲本间数量性状的综合遗传差异——遗传距离来预测吉林省爆玉米杂种一代的产量优势。 An experiment was conducted in 1990 to 1991 at the university,to study the relationships between genetic distance,cluster analysis and heterosis in popcorn(Zea mays var.everta).Results showed that there is no sense in cludtering parental lines for prediction of yield heterosis,but blood pedigree can beidentifed from cluster analysis.The relation between genetic divergence or distance and yield heterosis of F1 hybrids can be predicted from the genetic distances of their parental lines according to this model,but no definite relation could be found between parental genetic divergence and the quality heterosis of F1 hybrids.     

Investigation of genetic and morphological variation in the sago palm (Metroxylon sagu; Arecaceae) in Papua New Guinea

BACKGROUND AND AIMS: The genetic and morphological variation in the sago palm (Metroxylon sagu, Arecaceae) in Papua New Guinea (PNG) was investigated. METHODS: Amplified fragment length polymorphism (AFLP) was used to investigate the genetic structure of 76 accessions of M. sagu, collected in seven wild and semi-wild stands in PNG. KEY RESULTS: An analysis of ten quantitative morphological variables revealed that most of these were mutually correlated. Principal component analyses of the same morphological variables showed that neither armature (presence or absence of spines) nor geographical separation was reflected clearly in the quantitative morphological variation. Similarity matrices of genetic, quantitative morphological, geographical and armature data were tested for pair-wise correlations, using Mantel's test. The results only showed a significant correlation between genetic and geographical distances. Visual inspection of principal component analyses plots and a neighbour-joining dendrogram based on genetic distances supported this trend, whereas armature showed no relation with genetic distances. CONCLUSIONS: Geographical distribution defines some weak patterns in the genetic variation, whereas the genetic variation does not reflect any patterns in the morphological variation, including armature. The present study supports the accepted taxonomy of M. sagu, recognizing only one species of M. sagu in PNG.     

Characterization of MR (P) strains of Drosophila melanogaster: the number of intact P elements and their genetic effect.

To study the effect of mutagenic/carcinogenic agents on P-element transposition, the P strains used should be defined, especially with respect to the number of intact and functional P elements present. In this investigation, the relation between the number of complete P elements present in dysgenic males and P-insertion mutagenesis was studied in several MR (P) strains. The main conclusions from this investigation are: (1) Complete P elements can be present in the genome without genetic activity (even in a 'dysgenic' cross). As a consequence, the number of complete P elements present in particular dysgenic flies, is not necessarily an indication of their dysgenic genetic activity. (2) The MR-h12/Cy strain carries two complete P elements, one on the X chromosome without and one on the MR chromosome with genetic activity (making this strain most suitable for studies on P-transposition mechanisms).     

Highly recombinogenic regions at seed storage protein loci on chromosome 1DS of Aegilops tauschii, the D-genome donor of wheat

A detailed RFLP map was constructed of the distal end of the short arm of chromosome 1D of Aegilops tauschii, the diploid D-genome donor species of hexaploid wheat. Ae. tauschii was used to overcome some of the limitations commonly associated with molecular studies of wheat such as low levels of DNA polymorphism. Detection of multiple loci by most RFLP probes suggests that gene duplication events have occurred throughout this chromosomal region. Large DNA fragments isolated from a BAC library of Ae. tauschii were used to determine the relationship between physical and genetic distance at seed storage protein loci located at the distal end of chromosome 1DS. Highly recombinogenic regions were identified where the ratio of physical to genetic distance was estimated to be <20 kb/cM. These results are discussed in relation to the genome-wide estimate of the relationship between physical and genetic distance.     

Linking behavioral ecology with population genetics: insights from Drosophila nigrospiracula

Although Drosophila species provide important model systems for evolutionary biology, the ecologies and natural histories of most species are insufficiently characterized to permit predictions with respect to issues such as population genetic structure. A notable exception is the group of cactophilic Drosophila endemic to the Sonoran Desert of North America. One of these species, D. nigrospiracula, exhibits no population subdivision anywhere in its range. Here we present evidence suggesting that the timing of mating in relation to dispersal contributes to the panmixia observed in this species.