滇楸种质生长性状遗传变异及表型性状遗传多样性分析

为明确滇楸种质生长和表型性状的遗传变异程度及遗传多样性大小,提出合理的杂交育种策略。本研究对滇楸20个无性系进行了连年的生长性状测定,测量了其叶长、叶宽、皮孔长、皮孔宽、皮孔密度等表型性状。研究结果表明滇楸种质1、3、4和5 a树高及1~6 a胸径在无性系间差异均达显著水平。树高遗传变异系数和重复力随年份变化波动较大,胸径遗传变异系数和重复力年份间较为稳定,且重复力较高。表明滇楸种质胸径受遗传控制程度较大,且稳定性更高。滇楸种质叶长和叶宽遗传多样性指数较高,分别为2.016和2.012。皮孔性状遗传变异系数较高,皮孔长、皮孔面积和皮孔密度表型变异系数均超过20%,遗传变异系数均超过15%。说明滇楸种质表型变异较为丰富,具有较好的遗传改良基础。相关分析结果表明皮孔密度与生长呈负相关,皮孔大小与生长呈正相关。聚类分析将滇楸种质划分为4类,第Ⅰ类皮孔面积最大,密度最小;第Ⅱ类生长最慢,叶长最大;第Ⅲ类生长最快,叶形最宽;第Ⅳ类叶柄最长。     

大豆灰斑病菌DNA指纹图谱初步分析

大豆灰斑病菌具有明显的生理分化现象,鉴定病菌生理小种对于培育和推广抗病品种具有重要意义。从大豆灰斑病菌一毒力较强菌株的DNA基因组文库中筛选出2个含重复顺序的克隆,并用其对16个菌株的基因组DNA进行了Southern分析,获得了基因组特异的指纹图谱,对指纹图谱和毒力间的关系进行了初步比较。     

多重PCR检测CSF1PO,TPOX和TH01基因座在中国汉族中的多态性

短串联重复序列（ＳＴＲ）是由几个碱基对作为核心单位串联重复形成的一类ＤＮＡ序列,应用３个ＳＴＲ基因座在同一反应体系中进行互不干扰的多重ＰＣＲ,采用高分辨力的聚丙烯酰胺凝胶电泳分离、银染法显影技术,对我国汉族的ＣＳＦ１ＰＯ,ＴＰＯＸ和ＴＨ０１等３个基因座等位基因的基因频率调查,ＣＳＦ１ＲＯ基因座,观察到９个等位基因,２２个基因型;ＴＰＯＸ基因座,观察到６个等位基因,１４个基因型：ＴＨ０１基因座,观察到６个等位基因,１９个基因型。获得了满意的结果,显示了广阔的应用前景。     

以发育模块重复征用和整合为基础的进化创新机制

进化新征的起源和分化是进化发育生物学研究的核心问题。通过对多细胞生物早期发育调控机制的比较分析,发现亲缘关系较远的生物所共有的一些形态特征受保守的发育调控程序调节（深同源性）。许多创新性状的发生是基于对预先存在的基因或发育调控模块的重复利用和整合。发育基因调控网络在结构和功能上高度模块化,因此不仅可以通过模块拆分和重复征用改变发育程式,而且也增强了调控网络自身的进化力。研究基因调控网络和发育系统的进化动态将有助于更深入地认识生物演化过程中创新性状发生和表型进化的分子机制。     

航天诱变白桦生长性状分析

对15年生白桦航天搭载家系(HT-1、HT-2、HT-3、HT-4)及地面对照(CK-1、CK-2、CK-3、CK-4)的生长性状进行分析,并利用2年生、5年生及15年生的生长性状拟合生长曲线。结果表明:15年生HT-1和HT-4的树高分别与地面对照家系间差异达到了极显著水平和显著水平。其中,HT-1树高高于地面对照,而HT-4树高则低于地面对照。其余2个航天搭载家系的树高也高于对照家系,但未达到显著水平。随树龄的增长,航天搭载家系与地面对照的部分性状由差异显著变为差异不显著,但整体差异趋势依旧与苗期保持一致。航天搭载白桦家系及地面对照重复力除98-3家系外都属于高重复力水准(>0.5),HT-1树高性状的突变增益最高,为7.31%。以-x+S为标准在HT-1内选择了4株优良单株,最优单株树高比地面对照家系提高了35.29%。通过拟合树高生长曲线预测了树高生长的趋势。     

晚稻种子在温度激变处理后植株生育的变化

1956年夏天,我们为了进一步克服运作晚稻移植时受高温的影响返青慢发棵(?)的毛病,五月间将运作晚稻已萌发的种子在室温与高温(50°C)相间的条件下重复处理15天,观察其是否产生新的抗逆力。现将我们的试验过程与试验结果叙述于下面,不常之處希同志们给予友谊的批评。     

拟南芥叶绿体DNA全序列微卫星分布规律的分析

为进一步以拟南芥为模板,开发果树通用的叶绿体微卫星或称简单序列重复（chloroplast simple sequence repeat, cpSSR）引物,对拟南芥叶绿体DNA全序列cpSSR进行了统计分析.结果表明,拟南芥cpSSR以单碱基重复为主,占总数的78.6%,二碱基重复占总数的19%,三碱基重复占2.4%,三碱基以上重复为零.在单碱基重复中,又以A和T重复为主,占98.5%.二碱基重复全部为AT重复.单碱基重复中的纯粹重复41个,占总数的62.1%.间断重复数为23个,占总数的34.8%.复合重复数仅为2个.     

大卫鼠耳蝠线粒体控制区串联重复序列变异

中国特有种大卫鼠耳蝠线粒体D-loop区串联重复序列以81bp为重复单元,重复3～7次。54%的个体具有4个串联重复序列,与5～7个串联重复序列的现有模式具有较大的差异。重复单元的遗传差异受所在位次影响,具有明显的家族性或区域性特点。串联重复序列和相对保守的第一重复单元构建的ML树均形成了3个明显的分支,分别定名为东南区、西南区和南方区。线粒体重复序列区域间的差异暗示其可能经历了多次进化,并以东南区变异最为显著。     

长白落叶松种子园亲本无性系生长性状变异研究

东北地区多个长白落叶松（Larix olgensis）种子园已经营建多年,但亲本生长情况往往被忽视。本研究以汪清林业局49个长白落叶松亲本无性系为材料,对其多个生长性状进行测定与遗传变异分析,方差分析结果表明49个无性系间的各测定性状差异均达极显著水平,各测定性状表型变异系数和遗传变异系数变化范围分别为7.71%~31.93%和2.05%~12.55%,重复力变化范围为0.44~0.76,高重复力、高变异系数有利于无性系的评价选择;树高、胸径等大部分生长性状的相关性达极显著水平,表明各生长性状在生长发育中相互影响;主成分分析结果表明第一主成分贡献率为61.44%,主要代表生物量性状;依托主成分分析结果对长白落叶松亲本无性系进行综合评价,初步筛选L76、L5、L7、L12和L4等5个优良无性系,这些无性系树高等性状遗传增益变化范围为3.55%~15.50%,入选无性系可以为长白落叶松良种选育提供材料。     

重复序列PCR(rep-PCR)指纹分析技术在病原真菌鉴定和分型中的应用

随着医学科学的发展及人们对深部真菌感染的重视,越来越多的新技术用于临床真菌的检测和鉴定。重复序列PCR(rep-PCR)指纹分析技术因其高分辨力、快速、简便、经济等优势,已成为分析真菌基因组、明确菌属间克隆来源的重要方法。本文就rep-PCR指纹技术及其自动化DiversiLab System在病原真菌分类鉴定和流行病学研究中的应用加以综述。     

林木种源速生丰产势的研究

在数学上可用林木种源收获量分布曲线中超过某一收获量标准（如对照种源的平均收获量)的积分面积来表示林木种源获得速生丰产的可能性大小，这种可能性可以用来衡量林木种源的优劣。在林木种源试验中，由于参试种源的平均收获量水平和稳定性能的差异,各个林木种源均有其独特的收获量分布曲线，并均可求出各个种源相应的速生丰产积分面积或累积概率。本文提出用林木种源超过对照平均收获量的收获量累积概率值作为林木种源速生丰产综合性能优劣的一个指标，在各种源参试地点完全相同时，可用一个相应的参数--林木种源速生丰产势--来衡量和评价林木参试种源的优劣。     

PERMUTATION TESTS AND OUTGROUPS

Abstract — Commonly used permutation tail probability (PTP) and topology dependent permutation tail probability (T-PTP) tests incorporate an inappropriate treatment of designated outgroup taxa, and for that reason are biased either for (PTP) or for or against (T-PTP) rejection of the null hypothesis. A modified test is proposed, in which this source of bias is eliminated.     

EVOLUTIONARY RESCUE OF SEXUAL AND ASEXUAL POPULATIONS IN A DETERIORATING ENVIRONMENT

The environmental change experienced by many contemporary populations of organisms poses a serious risk to their survival. From the theory of evolutionary rescue, we predict that the combination of sex and genetic diversity should increase the probability of survival by increasing variation and thereby the probability of generating a type that can tolerate the stressful environment. We tested this prediction by comparing experimental populations of Chlamydomonas reinhardtii that differ in sexuality and in the initial amount of genetic diversity. The lines were serially propagated in an environment where the level of stress caused by salt increased over time from fresh water to the limits of marine conditions. In the long term, the combination of high diversity and obligate sexuality was most effective in supporting evolutionary rescue. Most of the adaptation to high‐salt environments in the obligate sexual‐high diversity lines had occurred by midway through the experiment, indicating that positive genetic correlations of adaptation to lethal stress with adaptation to sublethal stress greatly increased the probability of evolutionary rescue. The evolutionary rescue events observed in this study provide evidence that major shifts in ways of life can arise within short time frames through the action of natural selection in sexual populations.     

淡色库蚊酯酶等位基因及其在自然种群中的频率分布

酯酶基因扩增所产生的酯酶活性升高是库蚊Culex pipiens对有机磷杀虫剂抗性的主要机理之一。采用分子杂交技术和限制性酶切片段长度多态性(RFLP)分析,已鉴定出多种酯酶等位基因类型。该文通过酯酶基因特异性片段的PCR扩增及扩增片段的酶切片段分析,对淡色库蚊Culex pipiens pallens四种有机磷抗性品系的酯酶等位基因进行分型,并测定分析自然种群中不同酶型的频率分布。研究结果表明：PCR分型方法具有快速、准确的特点。不同的有机磷杀虫剂对酯酶等位基因具有明显的选择作用。双硫磷品系为B₁型;毒死蜱和敌百虫品系为B₂型;马拉硫磷品系为B₁型和B₁/B₂杂合型。不同地区采集的种群表现出不同的酶型频率分布。该文就杀虫剂对酯酶等位基因选择作用及自然种群的酶型频率分布进行了讨论。     

生态网络中物质、能量流动的时间链分析

本文以Ｍａｒｋｏｖ过程理论为基础,利用转移矩阵对生态网络中物质、能量流动和随机行为进行的描述;将输入的物质、能量在生态网络中宏观分布随时间的变化定义为物质、能量流动的时间链,并给一般生态网络中物质、能量流动时间链的分析方法。两个稳态生态网络中物质、能量流动的时间链分析表明,时间链直观地反映了物质、能量在流动中流失或耗散的宏观行为,由于物质再循机普遍存在,使得物质流动的时间链与能量流动的时间链有着质     

The probability of causation under a stochastic model for individual risk

In this paper we offer a mathematical definition for the probability of causation that formalizes the legal and ordinary-language meaning of the term. We show that, under this definition, even the average probability of causation among exposed cases is not identifiable from epidemiologic data. This is because the probability of causation depends both on the unknown mechanisms by which exposure affects disease risk and competing risks, and on the unknown degree of heterogeneity in the background disease risk of the exposed population. We derive the maximum and minimum values for the probability of causation consistent with the observable population quantities. We also derive the relationship of the "assigned share" (excess incidence rate as a proportion of total incidence rate) to the probability of causation.     

CENTRAL MOMENTS AND PROBABILITY DISTRIBUTION OF COLLESS'S COEFFICIENT OF TREE IMBALANCE

The great increase in the number of phylogenetic studies of a wide variety of organisms in recent decades has focused considerable attention on the balance of phylogenetic trees—the degree to which sister clades within a tree tend to be of equal size—for at least two reasons: (1) the degree of balance of a tree may affect the accuracy of estimates of it; (2) the degree of balance, or imbalance, of a tree may reveal something about the macroevolutionary processes that produced it. In particular, variation among lineages in rates of speciation or extinction is expected to produce trees that are less balanced than those that result from phylogenetic evolution in which each extant species of a group has the same probability of speciation or extinction. Several coefficients for measuring the balance or imbalance of phylogenetic trees have been proposed. I focused on Colless's coefficient of imbalance (7) for its mathematical tractability and ease of interpretation. Earlier work on this statistic produced exact methods only for calculating the expected value. In those studies, the variance and confidence limits, which are necessary for testing the departure of observed values of I from the expected, were estimated by Monte Carlo simulation. I developed recursion equations that allow exact calculation of the mean, variance, skewness, and complete probability distribution of I for two different probability-generating models for bifurcating tree shapes. The Equal-Rates Markov (ERM) model assumes that trees grow by the random speciation and extinction of extant species, with all species that are extant at a given time having the same probability of speciation or extinction. The Equal Probability (EP) model assumes that all possible labeled trees for a given number of terminal taxa have the same probability of occurring. Examples illustrate how these theoretically derived probabilities and parameters may be used to test whether the evolution of a monophyletic group or set of monophyletic groups has proceeded according to a Markov model with equal rates of speciation and extinction among species, that is, whether there has been significant variation among lineages in expected rates of speciation or extinction.     

Overfitting,generalization, and MSE in class probability estimation with high‐dimensional data

Accurate class probability estimation is important for medical decision making but is challenging, particularly when the number of candidate features exceeds the number of cases. Special methods have been developed for nonprobabilistic classification, but relatively little attention has been given to class probability estimation with numerous candidate variables. In this paper, we investigate overfitting in the development of regularized class probability estimators. We investigate the relation between overfitting and accurate class probability estimation in terms of mean square error. Using simulation studies based on real datasets, we found that some degree of overfitting can be desirable for reducing mean square error. We also introduce a mean square error decomposition for class probability estimation that helps clarify the relationship between overfitting and prediction accuracy.     

On the Theory of Partially Inbreeding Finite Populations. III. Fixation Probabilities under Partial Selfing When Heterozygotes Are Intermediate in Viability

In a previous paper by the senior author, an approximation to the probability of survival was given for a mutant, which is originally present in a single heterozygote, in a population that reproduces partly by selfing and partly by random mating. The population was assumed to be very large, but the result obtained is general with regard to the level of dominance in viability. In this paper two errors which were made in that earlier work are corrected. A general approximate expression is then derived for the probability that an allele A is fixed in a partially self fertilizing population of size N, if its initial frequency is p, selection is weak and heterozygotes with the allele are exactly intermediate in viability compared with genotypes AA and AA. A rigorous proof is given for a special case that is a generalization of the classical binomial sampling model. In this case, but not in general, the approximate fixation probability is independent of the probability of reproduction by selfing. Some implications are discussed.