The Geometry of Path Coefficients and Correlations

In the present paper, a generalized cosine formula is obtained for the difference between two angles in a k-dimensional Euclidean space, which is utilized to derive one of the principles of path analysis, namely, the correlation between two random variables is the sum of all connecting paths between them.     

Additive and Non-additive Genetic Correlations. II. Application to Data Obtained from a 12 × 12 Diallel Cross

The proposed genetic correlation analysis, that involves the partitioning of the overall genetic correlation into an additive and a non-additive component, has been applied to data obtained from a diallel experiment involving 12 white modified opaque-2 maize inbred lines. The correlation analysis provided an insight into possible indirect selection strategies for the improvement of inferior kernel quality traits associated with the opaque-2 gene. Direct selection for high yield and low vitreousness rating would provide an efficient selection strategy for the development of high-yielding modified opaque-2 maize hybrids with desirable endosperm traits. It was concluded that it is not necessary to conduct the density, hardness and breakability determinations.     

加性基因效应与分子标记回归方程的关系

控制数量性状的基因作用历来是遗传学工作者所关注的重要课题．本文对以正交表形式表现的共显性动物分子标记资料,根据加性效应基因控制的数量性状遗传模型配合了动物分子标记回归方程通式．结果表明：对以正交表形式表现的加性效应基因共显性分子标记资料配合的分子标记回归方程,可对加性等位基因的相对作用差加以估计,并可作为育种的依据．     

母体遗传效应对绒山羊生产性状遗传参数估计的影响

利用非求导约束最大似然法(DF-REML), 比较了内蒙古白绒山羊在两种不同动物模型下估计遗传参数的差异, 两种模型的区别在于是否考虑母体遗传效应。对两种模型的差异用似然比进行检验。结果表明, 母体遗传效应对于体重和绒厚影响极显著(P<0.01), 对于抓绒量、毛长、绒长度以及绒细度影响不显著(P>0.05)。     

Genetic and Maternal Variation for Heat Resistance in Drosophila from the Field

In Drosophila, field heritability estimates have focused on morphological traits and ignored maternal effects. This study considers heritable variation and maternal effects in a physiological trait, heat resistance. Drosophila were collected from the field in Melbourne, Australia. Resistance was determined using knock-down time at 37°. Drosophila melanogaster was more resistant than Drosophila simulans, and males tended to be more resistant than females. Field heritability and maternal effects were examined in D. simulans using the regression of laboratory-reared F(1) and F(2) onto field-collected parents. Males from the field were crossed to a laboratory stock to obtain progeny. The additive genetic component to variation in heat resistance was large and significant, and heritability was estimated to be around 0.5. A large maternal effect was also evident. Comparisons of regression coefficients suggested that the maternal effect was not associated with cytoplasmic factors. There was no correlation between body size (as measured by wing length) and heat resistance. Unlike in the case of morphological traits, the heritability for heat resistance in nature is not less than that measured in the laboratory.     

Laboratory Estimates of Heritabilities and Genetic Correlations in Nature

A lower bound on heritability in a natural environment can be determined from the regression of offspring raised in the laboratory on parents raised in nature. An estimate of additive genetic variance in the laboratory is also required. The estimated lower bounds on heritabilities can sometimes be used to demonstrate a significant genetic correlation between two traits in nature, if their genetic and phenotypic correlations in nature have the same sign, and if sample sizes are large, and heritabilities and phenotypic and genetic correlations are high.     

Chromosome Fragments in DICTYOSTELIUM DISCOIDEUM Obtained from Parasexual Crosses between Strains of Different Genetic Background

The first aneuploid strains of Dictyostelium discoideum have been unambiguously characterized, using cytological and genetic analysis. Three independently isolated, but genetically similar, fragment chromosomes have been observed in segregants from diploids formed between haploid strains derived from the NC4 and V12 isolates of D. discoideum. Once generated, the fragment chromosomes, all of which have V12-derived centromeres, can be maintained in a NC4 genetic background. Genetic evidence is consistent with the view that all three fragment chromosomes studied encompass the region from the centromere to the whiA locus of linkage group II and terminate in the interval between whiA and acrA. From cytological studies, one of the fragment chromosomes consists of approximately half of linkage group II.—We observed no deleterious effect on viability or asexual fruiting-body formation in either haploid or diploid strains carrying an additional incomplete chromosome and hence are disomic or trisomic, respectively, for part of linkage group II. The incomplete chromosome is lost at a frequency of 2 to 3% from disomic and trisomic strains, but surprisingly this loss is not increased in the presence of the haploidizing agent, benlate. A new locus (clyA), whose phenotype is altered colony morphology, is assigned to the region of linkage group II encompassed by the fragment chromosome.     

Genetic and Maternal Effects on Offspring Mortality in Mice

Trade-offs occur when two traits have opposing fitness effects such that positive selection on one trait is constrained by the negative fitness consequences of the other trait. To understand why trade-off may arise we need to study the genetic and non-genetic factors that influence associated traits because these may respond differently to selective pressure. Research into trade-offs has largely focused on the genetic basis of associated traits, yet both maternal effects and epigenetic effects have recently been shown to affect life history traits that play a role in trade-offs. In this study, we analyze genetic, epigenetic and life-history predictors of one of the most important trade-offs, that between offspring number and offspring mortality. Using a large-scale 3-generational intercross between two divergent mouse lines C57BL/6J and DBA/2J, we show that litter size differences between these lines, although significant, are surprisingly not the most important predictors of mortality. Offspring genotype, maternal effects and their interactions are the most influential factors determining mortality. We found significant paternal effects suggesting an important influence of paternal care or potentially the role of imprinted genes. Perhaps contrary to expectations our results further show that the trade-off between offspring number and mortality is not just a simple function of the two factors yielding, on average, an ‘optimal’ litter size at weaning. Indeed if one focused on litter size and mortality alone, the slope of relationship is the same for the two lines, yet they differ in the number of young at weaning. Our study reveals that a perceived trade-off between two traits is governed by a more complex set of interactions between genetic and non-genetic effects.     

Realized Sampling Variances of Estimates of Genetic Parameters and the Difference between Genetic and Phenotypic Correlations

A data set of 1572 heritability estimates and 1015 pairs of genetic and phenotypic correlation estimates, constructed from a survey of published beef cattle genetic parameter estimates, provided a rare opportunity to study realized sampling variances of genetic parameter estimates. The distribution of both heritability estimates and genetic correlation estimates, when plotted against estimated accuracy, was consistent with random error variance being some three times the sampling variance predicted from standard formulae. This result was consistent with the observation that the variance of estimates of heritabilities and genetic correlations between populations were about four times the predicted sampling variance, suggesting few real differences in genetic parameters between populations. Except where there was a strong biological or statistical expectation of a difference, there was little evidence for differences between genetic and phenotypic correlations for most trait combinations or for differences in genetic correlations between populations. These results suggest that, even for controlled populations, estimating genetic parameters specific to a given population is less useful than commonly believed. A serendipitous discovery was that, in the standard formula for theoretical standard error of a genetic correlation estimate, the heritabilities refer to the estimated values and not, as seems generally assumed, the true population values.     

Genetic variability in macaques: Correlations between biochemical and dermatoglyphic systems

The palmar dermatoglyphics of four groups of macaque, Macaca nemestrina, M. fuscata yakui, M. f. fuscata and M. fascicularis, were compared, and the genetic affinities of the four groups were assessed using a dermatoglyphic mean square distance measure. According to this measure the two subspecies of M. fuscata were dermatoglyphically more distant from one another than was M. fuscata fuscata from M. nemestrina, suggesting that the two insular populations of M. fuscata had evolved in genetic isolation. The distributions of specific dermatoglyphic patterns were then compared with the frequency distributions of alleles at different protein structural loci in other macaque populations. The results of the comparison were consistent in that insular populations showed reduction in variability for both kinds of systems. The implications of this correlation are discussed in terms of population size and natural selection.     

首例航天诱变玉米雄性不育突变体的遗传分析

将卫星搭载处理后代所得到的玉米雄性不育材料,在不同地点、不同年份、不同季节进行种植观察;从田间和室内对育性表现的稳定性进行鉴定。通过正交和反交对不育株的所属类型进行分析,结合自交、回交分析其遗传特点。结果表明,该不育材料的雄穗无任何花药外露,花药内无花粉粒,败育彻底,育性表现稳定,是一个由隐性单基因控制的可遗传的“无花粉型”核不育。     

Daunorubicin Derivatives Obtained from Daunorubicin and Nucleoside Dialdehydes

Abstract

Nucleoside dialdehydes were obtained by periodate oxidation of adenosine, cytidine, guanosine, uridine or 6-azauridine in the presence of Dowex (1×8; CH₃COO). Reductive alkylation of daunorubicin with these dialdehydes in the presence of NaBH₃CN produced a series of 3′-deamino-3′-(4-morpholino)daunorubicin or 13-(R, S)-dihydrodaunorubicin derivatives, the latter being mixtures of two diastereomers at 13-C atom. The morpholino-daunorubicin derivatives containing nucleic base moieties are less cytotoxic than cyanomorpholino-daunorubicin, morpholino-daunorubicin and even than the parent antibiotic.     

粳稻品质性状间及其与植株性状和产量性状间的遗传相关

利用朱军等提出的种子性状遗传模型,采用 3×3 NCⅡ正反交设计的亲本和部分组合F2代种子,分析了品质性状糙米率、垩白粒率、垩白面积和AC间及上述品质性状与株高、穗部性状等的遗传相关,以期为粳稻育种后代选择提供指导。结果表明,精米重与糙米率存在极显著的母体加性相关;虽然控制品质性状的主要遗传效应分量与植株性状相应遗传效应分量遗传协方差不显著,但在其他相应遗传效应分量方面存在着复杂的关系。     

Additive and Non-additive Genetic Correlations. I. Properties of Sampling Distributions

The sampling distributions of additive and non-additive genetic correlations estimated from a diallel experiment were determined through a computer simulation study. The properties of the sampling distributions were investigated in terms of the effect of varying the magnitude of the relevant variance components and the true correlation coefficient (Q), as well as the size of the diallel experiment. It was found that there was a high incidence of Q falling outside the range ?1 ≦Q≦1 when Q was close to 1 or -1, and the variance components were small. The degrees of freedom of the correlation components were shown to affect the variability of Q, and it was shown that a diallel experiment, that is to be used for a correlation analysis, should not be smaller than a 12 × 12 half diallel. Use of the Z transformation as a means of testing the significance of Q has been verified in this study and improvements on the degrees of freedom used for the transformation have been discussed.     

Estimation of Population Mean Under Successive Sampling Scheme when Various Weights and Regression Coefficients are Unknown

In this paper properties of an estimator of the population mean on current occasion under successive sampling scheme, when various weights (φh'S) and regression coefficients (βh,h-1) are estimated for h ≥ 2, have been studied. Some empirical results on the estimation of the variance of an unbiased estimator of population mean for h = 2 are also given.     

Spatial and Space-Time Correlations in Systems of Subpopulations with Genetic Drift and Migration

The geographic distribution of genetic variation is an important theoretical and experimental component of population genetics. Previous characterizations of genetic structure of populations have used measures of spatial variance and spatial correlations. Yet a full understanding of the causes and consequences of spatial structure requires complete characterization of the underlying space-time system. This paper examines important interactions between processes and spatial structure in systems of subpopulations with migration and drift, by analyzing correlations of gene frequencies over space and time. We develop methods for studying important features of the complete set of space-time correlations of gene frequencies for the first time in population genetics. These methods also provide a new alternative for studying the purely spatial correlations and the variance, for models with general spatial dimensionalities and migration patterns. These results are obtained by employing theorems, previously unused in population genetics, for space-time autoregressive (STAR) stochastic spatial time series. We include results on systems with subpopulation interactions that have time delay lags (temporal orders) greater than one. We use the space-time correlation structure to develop novel estimators for migration rates that are based on space-time data (samples collected over space and time) rather than on purely spatial data, for real systems. We examine the space-time and spatial correlations for some specific stepping stone migration models. One focus is on the effects of anisotropic migration rates. Partial space-time correlation coefficients can be used for identifying migration patterns. Using STAR models, the spatial, space-time, and partial space-time correlations together provide a framework with an unprecedented level of detail for characterizing, predicting and contrasting space-time theoretical distributions of gene frequencies, and for identifying features such as the pattern of migration and estimating migration rates in experimental studies of genetic variation over space and time.     

Maternal Genetic Composition of a Medieval Population from a Hungarian-Slavic Contact Zone in Central Europe

The genetic composition of the medieval populations of Central Europe has been poorly investigated to date. In particular, the region of modern-day Slovakia is a blank spot in archaeogenetic research. This paper reports the study of mitochondrial DNA (mtDNA) in ancient samples from the 9^th–12^th centuries originating from the cemeteries discovered in Nitra-Šindolka and Čakajovce, located in western Slovakia (Central Europe). This geographical region is interesting to study because its medieval multi-ethnic population lived in the so-called contact zone of the territory of the Great Moravian and later Hungarian state formations. We described 16 different mtDNA haplotypes in 19 individuals, which belong to the most widespread European mtDNA haplogroups: H, J, T, U and R0. Using comparative statistical and population genetic analyses, we showed the differentiation of the European gene pool in the medieval period. We also demonstrated the heterogeneous genetic characteristics of the investigated population and its affinity to the populations of modern Europe.     

Cytochrome b Genetic Diversity and Maternal Origin of Chinese Domestic Donkey

To clarify the origin of Chinese domestic donkeys, we investigated the mitochondrial Cytb gene from 244 animals from 13 native breeds. We found 55 variable sites in the Cytb gene sequence and subsequently defined 58 haplotypes. Analysis of haplotypes in combination with Cytb sequences revealed two mitochondrial origins in Chinese domestic donkeys, phenotypically expressed by the Somalian and Nubian lineages. The Somalian lineage predominated in Chinese domestic donkey breeds. Five specific Cytb gene SNPs diagnostic of each of the lineages were found in this study: 225(T-C), 237(C-T), 915(C-T), 1014(C-T), and 1134(A-G) mutations. They effectively distinguish the Nubian from the Somalian lineage in the mtDNA Cytb gene. Both lineages are from Africa and thus support the African maternal origins of Chinese domestic donkeys. No obvious geographic structure was found in Chinese domestic donkey breeds, but the population showed abundant genetic diversity.