杂交试验中误差的测验

在进行遗传学研究中 ,所采用的主要研究方法就是杂交试验法。遗传学家孟德尔正是利用豌豆作为试验材料 ,采用杂交试验法揭示出了遗传的 2个基本规律 ,即基因的分离规律和自由组合规律。在遗传试验中 ,如果对实验条件严加控制 ,而且试验的群体足够大 ,那么试验得出的实际数据就会与理论预期值非常接近。但由于种种因素的干扰 ,实际试验值偏离理论预期值而产生误差 ,总是在所难免的。那么试验中出现的误差 ,究竟是属于机会造成的 ,还是实验本身的问题 ?换句话说 ,出现的误差是否在理论允许的范围内 ?这就需要进行测验。而通常采用的方法是χ2 …     

关于“五个遗传学实验的一次杂交试验设计”一文的商榷

以果蝇为实验材料进行杂交实验来验证基本的遗传规律 ,是遗传学实验课教学中最经典的、最常用的方法［１～３］。不同的学校在进行这些实验时也都采用了各具特色的试验设计。我们在试验课教学中参考了陈宗礼先生发表在《遗传》杂志１９９６年第６期上的“五个遗传学实验的一次杂交试验设计”一文［４］,觉得这项设计构思新颖 ,是一个省时、省力 ,有利于培养学生分析能力的好方案 ,确有融会贯通 ,事半功倍的效果。对于论文中的一些不恰当的提法 ,虽然作者在《遗传》１９９７年第二期上有过更正［５］,但其部分实验数据仍值得商榷 ,在此与各位…     

核质杂交试验中用温度控制供体胚胎发育的尝试

以泥鳅为材料,成功地尝试了用温度调节供受精卵的发育速度,以求达到其在核质杂交中与受体在时间上的良好配合,泥鳅的受精卵在１３－３０℃之间的不同温度不发育至囊胚期,所需的时间差异达９小时,但囊胚细胞的成活率均在９０％以上。采用极化注射法将各温度组的囊胚细胞与泥鳅成熟的未受精卵进行核质杂交试验。均得到了成活的核质杂交鱼。从而提示：该方法是一种解决供体与受体时间配合的有效途径。     

杂交水稻直链淀粉含量遗传分析

杂交水稻稻谷是从Ｆ１代杂合体收获的Ｆ２代种子,由于Ｆ２代属分离群体,直链淀粉含量等稻米品质会发生分离现象．本研究选择直链淀粉含量低、中、高的５个亲本配组的５个杂交组合,按单粒分析法分析双亲亲本、Ｆ１和Ｆ２代的种子的直链淀粉含量．结果表明,Ｆ２代呈现１（低）：３（中＋高）孟德尔分离规律．在５个组合的单粒分析中发现分离的Ｆ２代群体呈双峰的连续分布,该现象表明高直链淀粉含量对低直链淀粉含量为不完全显性,除单一基因控制外,还受微效多基因修饰．因此杂交水稻育种工作中,尤其是优质杂交稻新组合选育时,必须注意选择双亲的直链淀粉含量基本一致,以防分离现象影响米质．     

在生理学研究中如何正确估计样本含量

目的：引起生理学研究人员对样本含量估计重要性的认识。方法：论述样本含量估计的意义及存在的问题,介绍常用的样本含量估计方法以及获取其他样本含量估计方法的途径。结果：清楚地表述了估计样本含量必需明白的基本概念、前提条件,并通过实例给出了两种场合下所需样本含量的估计过程和结果。结论：在估计样本含量时,必须明确资料将选用何种统计分析方法处理,并且应满足有关的前提条件,才能得到正确的估计结果。     

杂交中稻数量性状遗传因素的分析

本文主要研究了1985年到1990年间,全国杂交中稻区域试验的104个品种,并分析了13个数量性状遗传因素对杂交中稻产量的影响,得出影响杂交中稻产量的主要因素是：有效穗、总苗数、总粒数、结实率和全生育期等．还考察了在这些因素相互作用下,对杂交中稻产量的更深层次的影响.     

综合杂种优势的最优线性无偏预测

文献[1]提出综合杂种优势概念及经纬杂交试验设计中综合杂种优势的BLUE和置信区间;但把各配合力效应都视为固定效应,所得结论只能推断试验本身。为从同一经纬杂交试验获得更多信息,本文把各配合力效应视为随机效应,据混合线性模型理论,给出了经纬杂交设计中综合杂种优势的BLUP,可预测某品系与任一品系杂交的效果。本文还讨论了综合杂种优势的经济生物学基础,提出了确定目标性状及其相对经济价值的原理和方法,为实践中正确 使用综合杂种优势的理论和方法奠定基础。     

经纬杂交试验分析新法—一般最小二乘

经纬杂交试验主要涉及地方品种。这些品种具有两个显著特点:一是品种之内纯合程度较差,二是品种之间纯合程度不同。所以对于不同杂交组合而言,相应于观测值的误差效应不仅很大而且服从不同的分布;此时若再利用正规最小二乘进行分析,必然不能得到正确结果。本文根据客观特点,依据新的模型和最优线性无偏估计原理,对于这种试验提出了一种新的分析方法——一般最小二乘分析。这种方法只需首先估计各个组合的方差,然后用它对重复数和观测值进行校正,再按正规最小二乘分析步骤分析即可,所以并不复杂。具体使用有一实例说明。     

六倍体小黑麦与普通小麦杂交的细胞遗传学研究

利用六倍体小黑麦与普通小麦杂交,Ｆ１具有两个单倍体染色体组（Ｄ、Ｒ）,在减数分裂时,单倍的染色体组（Ｄ、Ｒ）可产生较多的单价体断裂与再融合。可诱发染色体易位,同时在杂种自交的情况下探讨单倍的Ｄ、Ｒ染色体组的遗传规律性与染色体组的再形成。１材料与方法１...     

A Semiparametric Estimator of the Crossing Point in the Two‐Sample Linear Shift Function: Application to Crossing Lifetime Distributions

Let X and Y be two random variables with continuous distribution functions F and G. Consider two independent observations X₁, … , X_m from F and Y₁, … , Y_n from G. Moreover, suppose there exists a unique x* such that F(x) > G(x) for x < x* and F(x) < G(x) for x > x* or vice versa. A semiparametric model with a linear shift function (Doksum, 1974) that is equivalent to a location‐scale model (Hsieh, 1995) will be assumed and an empirical process approach (Hsieh, 1995) is used to estimate the parameters of the shift function. Then, the estimated shift function is set to zero, and the solution is defined to be an estimate of the crossing‐point x*. An approximate confidence band of the linear shift function at the crossing‐point x* is also presented, which is inverted to yield an approximate confidence interval for the crossing‐point. Finally, the lifetime of guinea pigs in days observed in a treatment‐control experiment in Bjerkedal (1960) is used to demonstrate our procedure for estimating the crossing‐point. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Designing the Sample Size for Non-parametric,Multivariate Tolerance Regions

In supplementation of the work by ABT (1977, 1982) and ACKERMANN (1980, 1983) extensive ta.bles and approximite formulae are provided for the determination of the sample size for constructing “inner” and “outer” limits of non-parametric multivariate tolerance regions.     

Satellite Telemetry in Avian Research and Management: Sample Size Considerations

Abstract: Satellite tracking is currently used to make inferences to avian populations. Cost of transmitters and logistical challenges of working with some species can limit sample size and strength of inferences. Therefore, careful study design including consideration of sample size is important. We used simulations to examine how sample size, population size, and population variance affected probability of making reliable inferences from a sample and the precision of estimates of population parameters. For populations of >100 individuals, a sample >20 birds was needed to make reliable inferences about questions with simple outcomes (i.e., 2 possible outcomes). Sample size demands increased rapidly for more complex problems. For example, in a problem with 3 outcomes, a sample of >75 individuals will be needed for proper inference to the population. Combining data from satellite telemetry studies with data from surveys or other types of sampling may improve inference strength.     

On Use of Transformed Auxiliary Information in Probability Proportional to Size Method of Sample Selection

A probability proportional to size (PPS) method of sample selection, based on the transformed auxiliary information as the measure of size, has been suggested. It has been observed that the PPS estimator under the suggested method is always better than the simple random sampling with replacement (SRSWR) and the usual PPSWR estimator. The efficiency of the proposed estimator with respect to the estimators under reference has also been empirically compared.     

标记辅助回交育种中所需最小样本容量的近似估计

回交育种是把有利基因从供体亲本向受体亲本转移的一种有效方法,标记辅助选择可加速其进程。为了制定合理的标记辅助选择计划,育种家必须知道所需的后代群体大小。该文提出了一种估算在标记辅助回交育种中同时进行前景选择和背景选择所需群体大小的方法。在假定所需转移的目标基因座与遗传背景之间为相互独立的简化假设下,可以通过将解析方法（针对前景选择）与基于回交亲本图示基因型的模拟方法（针对背景选择）相结合,近似地估计出在每一世代中选到所需基因型的概率,进而估算出在一定概率水平下至少获得一个符合要求的个体所需的最小样本容量,用假想的例子演示了该方法的使用情况。该方法可以很方便地应用于实际的回交育种。     

Allocation of Sample Size to Strata and Related Problems

In this paper, we shall study an alternative method of deriving Neyman's Optimum allocation of sample size to strata for simple random sampling which is intuitive and simple. In order to obtain this allocation, the within stratum standard deviations of the study variate are required which are unknown and hence are substituted by known quantities. We shall discuss the effects of deviations from the optimum allocation and other related problems.     

样本量对云南松幼苗生物量模型构建及预估精度的影响

为探究不同样本量对生物量模型构建及建模精度的影响,以实际调查的20个家系,共615株云南松幼苗为例,通过编写计算机程序建立进行简单随机抽样,构建不同样本量云南松幼苗各器官及单株生物量异速生长方程。利用决定系数（R²）、估计值标准误（SEE）、均方根误差（RMSE）、总相对误差（RS）及平均误差绝对值（MAB）,对模型拟合优度与精度进行比较分析。结果表明：幂函数方程可较好地用于估测云南松幼苗生物量;随着样本量的增加模型精度评估指数MAB呈幂函数形式逐渐减小;当样本数量小于200时MAB较为敏感,模型精度较差,样本量大于200时,其精度随样本量逐渐增加,但变化幅度逐步减小并趋于稳定。因此,根据MAB的变化趋势,样本量达到200时可以构建精度较高且稳定模型。     

Reduction of Total Sample Size and Cost of Sampling in Tests of Hypothesis by Using Unequal Group Sizes

The standard approach in calculating the appropriate sample size required to detect a specified difference in the means of two populations for given type I and II errors assumes equal sample sizes in each group. It is shown here that equal sample sizes are usually sub-optimal with respect to total sample size and with respect to total cost of the experiment. This is may be important in experiments involving animals when costs are measured not only in monetary terms but also in terms of animal suffering or inconvenience.     

Sample Size Estimation in Cluster Randomized Studies with Varying Cluster Size

Cluster randomized studies are common in community trials. The standard method for estimating sample size for cluster randomized studies assumes a common cluster size. However often in cluster randomized studies, size of the clusters vary. In this paper, we derive sample size estimation for continuous outcomes for cluster randomized studies while accounting for the variability due to cluster size. It is shown that the proposed formula for estimating total cluster size can be obtained by adding a correction term to the traditional formula which uses the average cluster size. Application of these results to the design of a health promotion educational intervention study is discussed.     

Sample Size Influences the Variation of Invertebrate Diversity among Different Levels of a Stream Habitat Hierarchy

We quantified how sample size influences the variation of the diversity of caddisfly assemblages among different levels of a stream habitat hierarchy. Caddisflies were collected using a Surber sampler and these Surber units were used in a computer algorithm to generate samples in a variety of sample sizes. Our results show that the sample size has a primary role on how the variation of diversity among the levels of the habitat hierarchy is distributed. Thus, a practical implication of this study is that projects using different number of replicate samples cannot be directly compared. This finding calls the attention to the careful consideration of sampling issues in biodiversity assessment and monitoring (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)