染色体着丝点结构变化与习惯性流产的关系

为探讨染色体Cd结构变化与习惯性流产关系,采用Cd-NOR同步银染技术,对38例习惯性流产患者和42例正常人Cd结构变异、Cd结构消失、Cd结构最大横径和Cd-NOR融合进行测量和比较分析。发现习惯性流产患者的Cd结构变异和Cd结构消失的频率明显高于正常人,Cd结构最大横径明显小于正常人。Cd结构消失和Cd结构变异频率的增高以及Cd结构最大横径变小可能是影响习惯性流产的相关因素。 Abstract:To study the correlation between chromosome centromeric dots and habitual abortions,Cd variation,Cd loss,maximum diameter of Cd and Cd-NOR of 38 habitual abortion patients and 42 healthy persons were measured,compared and analysed with Cd-banding technique.It was found that the frequencies of Cd variation and Cd loss were obviously higher and maximum diameter of Cd was smaller in habitual abortion patients than those in healthy persons.The increase of frequencies of Cd variation and Cd loss and the decrease of maximum diameter of Cd might be the causes affecting habitual abortions.     

正常人胚胎绒毛细胞染色体着丝粒点(Cd)变异的研究

我们采用Cd-NOR同步银染技术,首次对正常人胚胎绒毛细胞染色体着丝粒点(Cd)变异作了研究,并将绒毛细胞染色体Cd变异与正常人外周血淋巴细胞体染色Cd变异进行了对比。在本研究中,我们观察到某些染色体存在Cd迟滞复制现象,并对此作了讨论。 Abstract:Centromeric dots(Cd)variation of chorion tissue chromosomes were studied by a simultaneous silver staining of both NOR and Cd.Comparison analysis of Cd variation for the chorionic villus samples and peripheral blood samples were carried out.We observe an event of Cd delaying reproduction and discuss the relation between the event and X chromosome delaying reproduction as well as chromosomeal nondisjunction.     

Genetic Variation and Clonal Diversity of the Two Divergent Types of Clonal Populations of Leymus chinensis Tzvel on the Song Liao Steppe in the West of Northeastern China

The genetic variation and clonal diversity of two divergent types (grey-green and yellow-green) of clonal populations of Leymus chinensis Tzvel at 14 loci were compared. Total gene diversity (HT) and the coefficient of genetic differentiation (GST) were all higher for the yellow-green type (HT = 0.270; GST =0.186) than for the grey-green type (HT = 0.250; GST = 0.157) of L. chinensis. Rare alleles usually occurred as heterozygotes rather than homozygotes and significant deviations from Hardy-Weinberg equilibrium were found only at a few loci. This indicated that these two types of populations were mainly out-crossing. Clonal diversity, evenness of clones, and mean clone size were not significantly different between the two types. We found that differences between the clone size and genetic variation of the yellow-green type of populations occurred with different climate and habitat population groups. However, for the grey-green type of populations, these genetic variations decreased under conditions of different climate and habitat population groups.     

Does sexual dimorphism vary by population? Laryngeal and ear anatomy in cricket frogs

Acoustic communication in many anuran species can show the effects of both natural and sexual selection. This is reflected in the sexually dimorphic an atomy of the lary nx and ear structures, as well as the allometric relationship of these morphological traits to head or body size. In this study, we examined laryngeal and ear structures of cricket frogs Acris crepitans not only as sexually dimorphic characteristics, but also as they differ across populations in environmentally different habitats. We used 2-way ANOVA to determine whether the volumetric or linear measurements of these structures differed by sex and population. Females have significantly larger body, head, and ear sizes, but significantly smaller larynges than males. Furthermore, females as well as males show larger body and head sizes, ears, and larynges in a dryer open habitat. An ANCOVA analysis shows that males, but not females, differ in laryngeal size across populations beyond the allometric changes attributable to head size alone indicating that males have a greater degree of laryngeal population variation. In contrast, our covariate analysis found that in both sexes many of the ear differences are non-sigrdficant once head size is accounted for, suggesting that most of the population-level ear variation is due to allometric effects of body size. We conclude that although both sexes show size differences in the larynx related to selection for larger body size in dry, open habitats, selection on males for larger larynx size related to the production of lower frequency calls in those habitats does not result in correlated changes in the female larynx. The results suggest that in anurans, selection for changes in body and head size affects both sexes equally, male calls and the vocal structures responsible for them can further diversify without concordant changes in females.     

Evolutionary importance of the relationship between cytogeography and climate:New insights on creosote bushes from North and South AmericaOA

Relationships between genome size and environmental variables suggest that DNA content might be adaptive and of evolutionary importance in plants.The genus Larrea provides an interesting system to test this hypothesis,since it shows both intra-and interspecific variation in genome size.Larrea has an amphitropical distribution in North and South American deserts,where it is most speciose.Larrea tridentata in North America shows a gradient of increasing autopolyploidy;while three of the four studi...     

Loss of heterozygosity by SCRaMbLEing

Genetic variation drives phenotypic evolution within populations. Genetic variation can be divided into different forms according to the size of genomic changes. However, study of large-scale genomic variation such as structural variation and aneuploidy is still limited and mainly based on the static, predetermined feature of individual genomes. Here, using SCRaMbLE,different levels of loss of heterozygosity(LOH) events including short-range LOH, long-range LOH and whole chromosome LOH were detected in evolved strains. By contrast, using rapid adaptive evolution, aneuploidy was detected in the adaptive strains. It was further found that deletion of gene GLN3, long-range LOH in the left arm of synthetic chromosome Ⅹ, whole chromosome LOH of synthetic chromosome Ⅹ, and duplication of chromosome Ⅷ(trisomy) lead to increased rapamycin resistance in synthetic yeast. Comparative analysis of genome stability of evolved strains indicates that the aneuploid strain has a higher frequency of degeneration than the SCRaMbLEd strain. These findings enrich our understanding of genetic mechanism of rapamycin resistance in yeast, and provide valuable insights into yeast genome architecture and function.     

Refuge size variation and potential for sperm competition in Wellington tree weta

Ecological variation in resources can in flue nee the distributi on and en counter rates of potential mates and competitors and, con sequently, the opport unity for sexual selection. Factors that influence the likelihood that females mate multiply could also affect the potential for sperm competition. In Wellington tree weta (Hemideina crassidens, plural "weta"), the size of tree cavities (called galleries) used as refuges affects weta distribution and thus the opport unity for sexual selection and selection on male weaponry size. We examined the predicted effects of gallery size and male weap onry size on the potential for sperm competition. We asked if gallery size in flue need the potential for multiple mating by females and potential for sperm competition, if male weaponry size was associated with relative expected sperm competition intensity (SCI), and if estimated male mating success was correlated with pote ntial SCI. To qua ntify relative competitive envir on merits of males, we created and analyzed networks of potential competitors based on which males could have mated with the same females. We found that small galleries had higher potential for female multiple mating and higher potential for sperm competition. Size of male weaponry was not associated with expected relative SCI. Regardless of gallery size, males with more potential mates were expected to face lower expected relative sperm competition. Thus, in this system, variation in the size of available refuges is likely to in flue nee the pote ntial for sperm competiti on, in a way that we might expect to in crease variation in overall reproductive success.     

Different paths to sexual size dimorphism in two praying mantids,Pseudomantis albofimbriata and Hierodula majuscula

Sexual size dimorphism （SSD） is widespread among diverse animal taxa and has attracted the attention of evolutionary biologists for over a century. SSD is likely to be adaptive and the result of divergent selection on different size optima for males and females, given their different roles in reproduction. The developmental trajectory leading to SSD may help us to understand how selection acts on male and female size. Here, we describe the growth and development of two Australian praying mantids, Pseudomantis albofimbriata and Hierodula majuscula including the number of moults, time to adulthood, size at each moult, and the degree of SSD. While both species exhibit the common pattern of female-biased SSD, the number of moults required for individuals to reach adulthood differed between males and females and between species. Despite their larger adult size, P. albofimbriata females require fewer moults and less time than males to reach adulthood, but are significantly larger than males from the second instar onwards. In contrast, H. majuscula males reached adulthood in fewer moults, and less time than females, however males and females did not differ in size until females went through their final moult into adulthood. H. majuscula also required more time and more moults to reach adulthood than 17. albofimbriata. We discuss these different developmental pathways in light of the existing knowledge of reproductive biology for each species. We also suggest that these differences may relate to the different phenologies that occur in strongly seasonal temperate environments compared with those in the tropics. This study provides evidence that SSD can result from two different patterns of growth and development in closely related species.     

The MNS16A polymorphism in the TERT gene in peri-centenarians from the Han Chinese population

MNS16A,a variable number of tandem repeats polymorphism in the TERT gene,has been suggested to regulate telomerase activity.As telomerase activity has been reported to be related to life-span,we hypothesized that this polymorphism might affect human longevity by controlling the length of the telomere.To test this hypothesis,we collected 446 unrelated pericentenarian individuals(age≥90,mean 94.45±3.45 years)and 332 normal controls(age 22-53,mean 35.0±12.0 years)from Dujiangyan,Sichuan,China.We typed the MNS16A polymorphism in both groups,and compared the allele and genotype frequencies between the peri-centenarian and control groups using the chi-squared test.There was no significant difference between the peri-centenarian and control groups.Thus,the MNS16A polymorphism in TERT might not influence human life-span,at least in the Han Chinese population studied here.     

Age and ovarian development are related to worker personality and task allocation in the ant Leptothorax acervorum

In social insects, workers of different morphological castes and age are known to act differently. Yet, it is unclear how body size and ovarian development influence worker personalities （i.e. consistent behavioral variation） and task allocation in similar aged ant workers of monomorphic species. Behavioral variation is thought to be a key element of division of labor, but few studies have linked worker personality to task allocation. We investigated individual behavior in Leptothorax acervorum ant workers at two time points during the first three months of their life and in two different settings. We observed worker behavior in the nest （i.e. task allocation） and in standardized aggression, exploration and brood care experiments （i.e. personality） and found behavioral repeatability in foraging and exploration. Further, workers acted consistently across settings： workers with a more ag gressive and exploratory personality type were more active in the nest. Moreover, ovarian development was associated with worker personality and task allocation： older workers with welldeveloped ovaries foraged less, but were more aggressive and exploratory. In accordance with the typical agepolyethism of social insects, workers became more active and foraged more as they grew older. Consequently, our study suggests that task allocation in Leptothorax acervorum is not only influenced by ovari an development and age, but moreover by the personalities of its workers .     

Variation in age composition among colony sizes in Cliff Swallows

Variation in group size is characteristic of most social species. The extent to which individuals sort among group sizes based on age may yield insight into why groups vary in size and the age‐specific costs and benefits of different social environments. We investigated the age composition of Cliff Swallow (Petrochelidon pyrrhonota) colonies of different sizes over 18 yr at a long‐term study site in western Nebraska, USA. Using years elapsed since banding as a relative measure of age for over 194,000 birds, we found that the proportion of age‐class‐1 swallows (birds banded as nestlings or juveniles or adults in the year of banding) of both sexes increased in larger colonies and at colony sites becoming active later in the summer. Age composition was unrelated to how often a particular colony site was used. The effect of colony size most likely reflected the fact that older birds return to the same colony site in successive years even when the colony size there decreases, and that yearlings and immigrants benefit more from larger colonies than do older, more experienced individuals. The date effect probably resulted in part from later spring arrival by younger and/or immigrant swallows. At fumigated sites where ectoparasitic swallow bugs (Oeciacus vicarius) had been removed, age composition did not vary with either colony size or colony initiation date. The patterns reported here appear to be driven partially by the presence of ectoparasites and suggest that the hematophagous bugs influence variation in Cliff Swallow group composition. Our results are consistent with the hypothesis that variation in colony size reflects, in part, age‐based sorting of individuals among groups.     

Heat stress and age induced maternal effects on wing size and shape in parthenogenetic Drosophila mercatorum

Maternal effects on progeny wing size and shape in a homozygous parthenogenetic strain of Drosophila mercatorum were investigated. The impact of external maternal factors (heat stress) and the impact of internal maternal factors (different maternal and grand maternal age) were studied. The offspring developed under identical environmental conditions, and due to lack of genetic variation any phenotypic difference among offspring could be ascribed to maternal effects. Wing size was estimated by centroid size, shape was analysed with the Procrustes geometric morphometric method and variation in landmark displacement was visualized by principal component analysis. Both kinds of maternal effects had a significant impact on progeny wing size and shape. Maternal heat stress led to the same pattern of response in size and shape among the progeny, with increased difference between the control group and progeny from heat stressed flies in both size and shape with increased maternal heat stress temperature. The effects of maternal age, however, led to different responses in size and shape between the different progeny groups. The observed variation in landmark displacements was similar, and in both cases mainly associated with shape differences of the posterior part of the wing. Finally, our results suggest that maternal effect has some evolutionary implications by altering the genetic correlations among traits, which can affect the response to selective pressures.     

Which factors contribute most to genome size variation within angiosperms?

Genome size varies greatly across the flowering plants and has played an important role in shaping their evolution. It has been reported that many factors correlate with the variation in genome size, but few studies have systematically explored this at the genomic level. Here, we scan genomic information for 74 species from 74 families in 38 orders covering the major groups of angiosperms (the taxonomic information was acquired from the latest Angiosperm Phylogeny Group (APG IV) system) to evaluate the correlation between genome size variation and different genome characteristics: polyploidization, different types of repeat sequence content, and the dynamics of long terminal repeat retrotransposons (LTRs). Surprisingly, we found that polyploidization shows no significant correlation with genome size, while LTR content demonstrates a significantly positive correlation. This may be due to genome instability after polyploidization, and since LTRs occupy most of the genome content, it may directly result in most of the genome variation. We found that the LTR insertion time is significantly negatively correlated with genome size, which may reflect the competition between insertion and deletion of LTRs in each genome, and that the old insertions are usually easy to recognize and eliminate. We also noticed that most of the LTR burst occurred within the last 3 million years, a timeframe consistent with the violent climate fluctuations in the Pleistocene. Our findings enhance our understanding of genome size evolution within angiosperms, and our methods offer immediate implications for corresponding research in other datasets.     

The best in all possible worlds? A quantitative genetic study of geographic variation in the meadow vole,Microtus pennsylvanicus

The meadow vole, Microtus pennsylvanicus , is the most widely distributed Microtus species in North America. Across its range, it shows marked demographic differences, experiences a large range of climatic conditions, and varies considerably in body size and life-history characteristics. To study the genetic basis of the geographic variation in size and life history of this species, we subjected three populations, one from central Canada and two from eastern Canada, to quantitative genetic analysis in the lab. We studied the variance and covariance of several size and growth variables as well as age and size at maturity by means of population crosses, full-sib analysis, and parent-offspring regressions. We found that the phenotypic differences among these populations are almost entirely due to environmental effects. However, within populations, additive genetic and maternal effects explain most of the variation. We discuss possible explanations for the lack of genetic differences among the populations and speculate that a similar reaction norm is maintained in all populations through heterogeneity in the temporal or spatial environment that the populations experience. The heterogeneity may be mediated through population density fluctuations, climatic variation, or variation in site productivity. Thus, we hypothesize that M. pennsylvanicus has evolved to be the best in all possible worlds rather than in one actual world. This study highlights the crucial importance of maternal and environmental effects on the size, growth, and life history of small rodents.     

Body mass index and chronic energy deficiency of adult males of Central Indian populations

Data on body weight, height, and sitting height from 11,496 adult males, age 18-62 years, belonging to 38 different populations of five major social groups (scheduled tribes, scheduled castes, "other backward castes," general castes, and Muslims) of Central India were taken for our analysis to assess the nutritional status of these groups. Cormic index and body mass index (BMI) were computed, and an analysis of variance (ANOVA) was carried out among different populations as well as among social groups separately on Cormic index and BMI. Shape, size, and generalized distances among the different social groups were computed and dendrograms were drawn. The level of malnutrition is the lowest among the general castes. The opposite is the case with the scheduled castes and scheduled tribes. Comparison of the coefficient of variation shows that there is variation in weight and BMI but that there is no marked variation in the other anthropometric variables. The ANOVA on Cormic index and BMI suggests that the people within a population are more homogeneous than the people between populations. There is a positive but statistically insignificant correlation between Cormic index and BMI. The five social groups differ more in size distance than in shape distance. According to the dendrogram of generalized distance values, the Muslims and the general castes can be grouped into one cluster and the scheduled castes, scheduled tribes, and other backward castes can be grouped into another cluster.     

Pole age affects cell size and the timing of cell division in Methylobacterium extorquens AM1

A number of recent experiments at the single-cell level have shown that genetically identical bacteria that live in homogeneous environments often show a substantial degree of phenotypic variation between cells. Often, this variation is attributed to stochastic aspects of biology-the fact that many biological processes involve small numbers of molecules and are thus inherently variable. However, not all variation between cells needs to be stochastic in nature; one deterministic process that could be important for cell variability in some bacterial species is the age of the cell poles. Working with the alphaproteobacterium Methylobacterium extorquens, we monitored individuals in clonally growing populations over several divisions and determined the pole age, cell size, and interdivision intervals of individual cells. We observed the high levels of variation in cell size and the timing of cell division that have been reported before. A substantial fraction of this variation could be explained by each cell's pole age and the pole age of its mother: cell size increased with increasing pole age, and the interval between cell divisions decreased. A theoretical model predicted that populations governed by such processes will quickly reach a stable distribution of different age and size classes. These results show that the pole age distribution in bacterial populations can contribute substantially to cellular individuality. In addition, they raise questions about functional differences between cells of different ages and the coupling of cell division to cell size.     

Size Matters: Individual Variation in Ectotherm Growth and Asymptotic Size

Body size, and, by extension, growth has impacts on physiology, survival, attainment of sexual maturity, fecundity, generation time, and population dynamics, especially in ectotherm animals that often exhibit extensive growth following attainment of sexual maturity. Frequently, growth is analyzed at the population level, providing useful population mean growth parameters but ignoring individual variation that is also of ecological and evolutionary significance. Our long-term study of Lake Erie Watersnakes, Nerodia sipedon insularum, provides data sufficient for a detailed analysis of population and individual growth. We describe population mean growth separately for males and females based on size of known age individuals (847 captures of 769 males, 748 captures of 684 females) and annual growth increments of individuals of unknown age (1,152 males, 730 females). We characterize individual variation in asymptotic size based on repeated measurements of 69 males and 71 females that were each captured in five to nine different years. The most striking result of our analyses is that asymptotic size varies dramatically among individuals, ranging from 631–820 mm snout-vent length in males and from 835–1125 mm in females. Because female fecundity increases with increasing body size, we explore the impact of individual variation in asymptotic size on lifetime reproductive success using a range of realistic estimates of annual survival. When all females commence reproduction at the same age, lifetime reproductive success is greatest for females with greater asymptotic size regardless of annual survival. But when reproduction is delayed in females with greater asymptotic size, lifetime reproductive success is greatest for females with lower asymptotic size when annual survival is low. Possible causes of individual variation in asymptotic size, including individual- and cohort-specific variation in size at birth and early growth, warrant further investigation.     

Variation in Age and Size in Fennoscandian Three-Spined Sticklebacks (Gasterosteus aculeatus)

Average age and maximum life span of breeding adult three-spined sticklebacks (Gasterosteus aculeatus) were determined in eight Fennoscandian localities with the aid of skeletochronology. The average age varied from 1.8 to 3.6 years, and maximum life span from three to six years depending on the locality. On average, fish from marine populations were significantly older than those from freshwater populations, but variation within habitat types was large. We also found significant differences in mean body size among different habitat types and populations, but only the population differences remained significant after accounting for variation due to age effects. These results show that generation length and longevity in three-spined sticklebacks can vary significantly from one locality to another, and that population differences in mean body size cannot be explained as a simple consequence of differences in population age structure. We also describe a nanistic population from northern Finland exhibiting long life span and small body size.     

Is there a threshold size regulating seaward migration of brown trout and Atlantic salmon?

We investigated the influence of variation in body size and growth rate on age of smolting in Atlantic salmon and brown trout in four different Norwegian rivers. In Atlantic salmon smolt ages varied between 2 and 6 years, and in brown trout between 2 and 7 years. Smolt age was negatively correlated with parr growth, and positively correlated with smolt size. Age at smolting was more variable in the two northern than the two southern rivers. Smolt sizes and ages were also more variable in brown trout than in Atlantic salmon. Based on the observed variation in smolt size and age, we reject the hypothesis that a threshold size alone regulates age at smolting. Within populations smolt age depends on growth rate so that fast-growing parr smolted younger and smaller than slow-growing parr. We hypothesize that smolt size and age is a trade-off between expected benefits and costs imposed by differences in individual growth rate.