Estimates of marker-associated QTL effects in Monte Carlo backcross generations using multiple regression

Summary The decision of whether or not to use QTLassociated markers in breeding programs needs further information about the magnitude of the additive and dominance effects that can be estimated. The objectives of this paper are (1) to apply some of the Moreno-Gonzalez (1993) genetic models to backcross simulation data generated by the Monte Carlo method, and (2) to get simulation information about the number of testing progenies and mapping density in relation to the magnitude of gene effect estimates. Results of the Monte Carlo study show that the stepwise regression analysis was able to detect relatively small additive and dominance effects when the QTL are independently segregating. When testing selfed families derived from backcross individuals, dominance effects had a larger error standard deviation and were estimated at a lower frequency. Linked QTL require a higher marker mapping density on the genome and a larger number of progenies to detect small genetic effects. Reduction of the environmental error variance by evaluating selfed backcross families in replicate experiments increased the power of the test. Expressions of the number of progenies for detecting significant additive effects were developed for some genetic situations. The ratio of the within-backcross genetic variance to the square of a gene effect estimate is a function of the number of progenies, the heritability of the trait, the marker map density and the portion of the genetic variance explained by the model. Different values (from 0 to 1) assigned to (relative position of the QTL in the marker segment) did not cause a large shift in the residual mean square of the model.     

Kin-structured migration and the rate of advance of an advantageous gene

Hemoglobin E, an allele generally considered to confer malarial resistance in heterozygotes, is found in high frequencies across a wide area of Southeast Asia. Apparently it originated as a single-point mutation which was spread by gene flow. The rate of diffusion of this adaptive allele is studied using four computer simulation models. It is shown that in small populations deterministic equations for gene flow may overestimate rates of diffusion. Other aspects of population structure, however, such as kin-structuring of migrant groups, increase the rate of advance. Finally, population growth coupled with the spread of the allele leads to much more rapid diffusion. These results suggest that population structure can be an important factor affecting the diffusion of advantageous genes.     

Factor-free and one-factor-promoted poly(U,C)-dependent synthesis of polypeptides in cell-free systems from Escherichia coli

α-Tropomyosin from rat cardiac muscle was shown by two-dimensional gel electrophoresis to become phosphorylated when tissue slices were incubated in Eagle's medium supplemented with ³²P_i. In the adult rat and mouse heart the level of phosphorylation was ～30%, but the level was much higher in the foetal heart (60–70%). A similar developmental trend was observed in skeletal muscle from the rat and mouse, where phosphorylated forms of both α- and β-tropomyosins were observed. When rat cardiac cells were grown in tissue culture in the presence of ³²P_i, radioactivity was incorporated into the region of the gel containing tropomyosin.     

The use of bridging systems to increase genetic variability in compound chromosome strains for genetic control of Lucilia cuprina (Wiedemann)

Summary Genetic variability in the non-compound portion of the genomes of compound-chromosome (CC) strains intended for genetic control can be increased by the use of bridging strains which can be crossed to both CC and normal strains. Two bridging systems are described for chromosome-5 CC strains of Lucilia cuprina. The first system relies on the established viability and fertility of males trisomic for chromosome 5R. Males carrying the (5L.YL)23 half-translocation, a C(5R), and a normal chromosome 5 were crossed successfully to a CC strain and a normal strain. The second system uses a pair of reciprocal whole-arm 4;5 translocations to generate gametes disomic for 5R and nullosomic for 5L, which in combination with C(5L)-bearing gametes form viable near-euploid offspring with only small duplications and deficiencies. These offspring (C(5L); (4L.5R)357; (4R.5R)194; (4L.4R)) were crossed successfully with both CC and T(4;5)357/ + individuals. The latter were in turn crossed successfully with normal strains. The T(Y;5)23 system allows replacement of the non-CC genome with wild material more rapidly than the T(4;5)357/T(4;5)194 system, but unlike the latter does not allow replacement of the Y chromosome in the CC strain. The double translocation system is currently being used in L. cuprina.     

Hysteresis,oscillations, and pattern formation in realistic immobilized enzyme systems

Summary Hysteresis, oscillations, and pattern formation in realistic biochemical systems governed by P.D.E.s are considered from both numerical and mathematical points of view. Analysis of multiple steady states in the case of hysteresis, and bifurcation theory in the cases of oscillations and pattern formation, account for the observed numerical results. The possibility to realize these systems experimentally is their main interest, thus bringing further arguments in favor of theories explaining basic biological phenomena by diffusion and reaction.     

Parameter identification of the calvin photosynthesis cycle

Summary This article is concerned with the determination of kinetic parameters of the Calvin photosynthesis cycle which is described by seventeen nonlinear ordinary differential equations. It is shown that the task requires dynamic data for several sets of initial conditions. The numerical technique is based upon an algorithm for non-linear optimization and Gear's numerical integration scheme for stiff systems of differential equations. The sensitivity of the parameters to noise in the data is tested with a method adapted from Rosenbrook and Storey. A preliminary set of parameters has been obtained from a preliminary set of experimental data. The numerical methods are then tested with synthetic data derived from these parameters. The mathematical model and the results obtained in the simulation are used as an aid in designing new experiments.     

Nature and origin of patterns of changes in cell shape in embryos

Spatial patterns of the future elongation of cells exist in the early embroyo. In the newt, such a pattern of changers of cell shape contributes to the formation of the neural plate. Regardless of where neural plate. Regardless of where neural plte cells are transplanted, they change shape as prescribed by tge pattern. Embryonic induction has a role in establishing this pattern.     

Guidelines for model adaptation: A study of the transferability of a general seagrass ecosystem Dynamic Bayesian Networks model

In general, it is not feasible to collect enough empirical data to capture the entire range of processes that define a complex system, either intrinsically or when viewing the system from a different geographical or temporal perspective. In this context, an alternative approach is to consider model transferability, which is the act of translating a model built for one environment to another less well‐known situation. Model transferability and adaptability may be extremely beneficial—approaches that aid in the reuse and adaption of models, particularly for sites with limited data, would benefit from widespread model uptake. Besides the reduced effort required to develop a model, data collection can be simplified when transferring a model to a different application context. The research presented in this paper focused on a case study to identify and implement guidelines for model adaptation. Our study adapted a general Dynamic Bayesian Networks (DBN) of a seagrass ecosystem to a new location where nodes were similar, but the conditional probability tables varied. We focused on two species of seagrass (Zostera noltei and Zostera marina) located in Arcachon Bay, France. Expert knowledge was used to complement peer‐reviewed literature to identify which components needed adjustment including parameterization and quantification of the model and desired outcomes. We adopted both linguistic labels and scenario‐based elicitation to elicit from experts the conditional probabilities used to quantify the DBN. Following the proposed guidelines, the model structure of the general DBN was retained, but the conditional probability tables were adapted for nodes that characterized the growth dynamics in Zostera spp. population located in Arcachon Bay, as well as the seasonal variation on their reproduction. Particular attention was paid to the light variable as it is a crucial driver of growth and physiology for seagrasses. Our guidelines provide a way to adapt a general DBN to specific ecosystems to maximize model reuse and minimize re‐development effort. Especially important from a transferability perspective are guidelines for ecosystems with limited data, and how simulation and prior predictive approaches can be used in these contexts.     

CRISPR/Cas系统的分类及研究现状

CRISPR技术作为一种新型的基因编辑技术,被广泛应用于微生物、动物和植物领域。对CRISPR/Cas系统的起源、分类特点等进行了阐述,重点梳理了CRISPR/Cas系统分类的发展历程,并根据最新分类方法,介绍了不同类型的CRISPR/Cas系统的作用机制、内部不同蛋白的作用特点及应用与发展,以期探寻更多的CRISPR/Cas系统,扩大该系统的应用领域。     

不同放牧制度下呼伦湖流域草原植被冠层截留

冠层截留是降雨过程中的水量分配和流域水平衡的一个重要组成部分,通过水浸泡法和降雨模拟实验研究呼伦湖流域草原3种放牧制度下(休牧、轮牧、自由放牧(超载放牧))植被冠层截留量的变化规律,并利用遥感解译植被归一化指数(NDVI),确定3种放牧制度下草原面积,估算呼伦湖流域草原降雨截留量。研究表明:在休牧、轮牧、自由放牧3种制度下,水浸泡法测定的截留量分别是0.468、0.320、0.271 mm。降雨模拟实验法测得的结果分别是0.957、0.613、0.431 mm。休牧、轮牧、自由放牧草场叶面积指数、盖度、容重、生物量等指标差异显著(P0.05),且单株植被高度、鲜重对截留量影响显著呈线性正相关关系。呼伦湖流域草原一次降雨量为大于等于30 mm全流域降雨,其植被截留量为6.462×106m3。