猪CAST基因的遗传多态性及遗传效应分析

采用PCR—SSCP方法对猪cAST基因遗传多态性进行分析。并研究基因型与肉质性状和背膘厚的相关性。根据猪CAST基因的cDNA序列（M20160）设计7对引物。结果在F1／R1。F6／R6引物对扩增的片段上发现了多态性。并对纯合子进行测序。发现317位A—G突变。2042位G—C突变。基因型在不同猪种分布的多重比较结果表明。长白猪、大白猪和杜洛克猪与沂蒙黑猪和莱芜猪比较差异极显著（P〈0．01）。固定效应模型分析结果表明,嫩度及背膘厚基因型间差异显著（P〈0．05）,而pH值、温度及滴水损失基因型间差异不显著（P〉0．05）。最小二乘分析结果表明,不同猪种比较,屠宰12h和24h后肌肉温度、30min和1h后pH值及滴水损失差异显著（P〈0．05）;BBCC和BBDD单元型个体与其他单元型个体比较肌肉嫩度的差异显著（P〈0．01）。AACC和AADD单元型个体与其他单元型个体比较背膘厚的差异显著（P〈0．01）。因此,推测CAST基因对猪肉品质及背膘厚存在一定的影响。将CAST基因应用于猪育种过程中的标记辅助选择将可以改善猪肉品质。加快猪的育种进程。     

GENETIC ENGINEERING TO AVOID GENETIC NEGLECT: FROM CHANCE TO RESPONSIBILITY

Currently our assessment of whether someone is a good parent depends on the environmental inputs (or lack of such inputs) they give their children. But new genetic intervention technologies, to which we may soon have access, mean that how good a parent is will depend also on the genetic inputs they give their children. Each new piece of available technology threatens to open up another way that we can neglect our children. Our obligations to our children and our susceptibilities to corresponding legal and moral sanctions may be about to explosively increase. In this paper I argue that we should treat conventional neglect and ‘genetic neglect’– failing to use genetic intervention technologies to prevent serious diseases and disabilities – morally consistently. I conclude that in a range of cases parents will have a moral obligation to use genetic treatments to prevent serious disabilities in their children. My particular focus is on prenatal interventions and their impact of the bodily integrity of expectant mothers. I conclude that although bodily integrity constrains moral obligations, it is outweighed in a range of cases.     

GENETIC DRIFT AND COLLECTIVE DISPERSAL CAN RESULT IN CHAOTIC GENETIC PATCHINESS

Chaotic genetic patchiness denotes unexpected patterns of genetic differentiation that are observed at a fine scale and are not stable in time. These patterns have been described in marine species with free‐living larvae, but are unexpected because they occur at a scale below the dispersal range of pelagic larvae. At the scale where most larvae are immigrants, theory predicts spatially homogeneous, temporally stable genetic variation. Empirical studies have suggested that genetic drift interacts with complex dispersal patterns to create chaotic genetic patchiness. Here we use a coancestry model and individual‐based simulations to test this idea. We found that chaotic genetic patterns (qualified by global F_ST and spatio‐temporal variation in F_ST's between pairs of samples) arise from the combined effects of (1) genetic drift created by the small local effective population sizes of the sessile phase and variance in contribution among breeding groups and (2) collective dispersal of related individuals in the larval phase. Simulations show that patchiness levels qualitatively comparable to empirical results can be produced by a combination of strong variance in reproductive success and mild collective dispersal. These results call for empirical studies of the effective number of breeders producing larval cohorts, and population genetics at the larval stage.     

龙牙木天然种群遗传多样性及遗传分化

采用水平切片淀粉凝胶电泳测定东北地区分布的4 个龙牙木种群的遗传结构。统计分析了10 个酶系统的11 个位点, 结果表明:龙牙木种群内存在着丰富的遗传变异, 多态位点百分率72.73%, 等位基因平均数为1.72, 期望杂合度为0.5617, 遗传一致度和遗传距离为0.9865和0.0133。这个结果与前文对其形态特征和薄层色谱特征分析所得结果基本一致, 充分说明区域龙牙木属于同一种物种的两个变种。     

GENETIC CONTROL OF CYTODIFFERENTIATION

The cells of the anterior region of the larval fatbody of Drosophila melanogaster accumulate kynurenine at the end of the third larval instar, whereas the cells of the posterior region are involved in pteridine metabolism. Through a series of transplantation experiments it has been demonstrated that the anterior fat cells synthesize kynurenine. The mutant vermilion lacks kynurenine, and the anterior fat cells of this mutant strain lack the autofluorescence characteristic of kynurenine. When the non-allelic suppressor gene is combined with vermilion, the synthesis of kynurenine is restored in the anterior fat cells, and some of the cells of the posterior region contain kynurenine as well. A similar extension in the number of cells containing kynurenine can be induced in the normal Ore-R strain by feeding the precursor tryptophan. It has been concluded that the absence of a physiological process in a differentiated cell does not necessarily represent a loss of the genetic potential for that process. The normal allele at the suppressor locus inhibits the occurrence of kynurenine in the posterior fat cells, whereas the mutant allele su²-s allows the expression of this potential. An inducer such as tryptophan can overcome this inhibition in the normal strain, and as a result the cells which are normally differentiated as "isoxanthopterin cells" may produce kynurenine as well.     

EPISTASIS BETWEEN NEW MUTATIONS AND GENETIC BACKGROUND AND A TEST OF GENETIC CANALIZATION

Abstract The importance for fitness of epistatic interactions among mutations is poorly known, yet epistasis can exert important effects on the dynamics of evolving populations. We showed previously that epistatic interactions are common between pairs of random insertion mutations in the bacterium Escherichia coli . In this paper, we examine interactions between these mutations and other mutations by transducing each of twelve insertion mutations into two genetic backgrounds, one ancestral and the other having evolved in, and adapted to, a defined laboratory environment for 10,000 generations. To assess the effect of the mutation on fitness, we allowed each mutant to compete against its unmutated counterpart in that same environment. Overall, there was a strong positive correlation between the mutational effects on the two genetic backgrounds. Nonetheless, three of the twelve mutations had significantly different effects on the two backgrounds, indicating epistasis. There was no significant tendency for the mutations to be less harmful on the derived background. Thus, there is no evidence supporting the hypothesis that the derived bacteria had adapted, in part, by becoming buffered against the harmful effects of mutations.     

ESTIMATING RELATEDNESS USING GENETIC MARKERS

A new method is described for estimating genetic relatedness from genetic markers such as protein polymorphisms. It is based on Grafen's (1985) relatedness coefficient and is most easily interpreted in terms of identity by descent rather than as a genetic regression. It has several advantages over methods currently in use: it eliminates a downward bias for small sample sizes; it improves estimation of relatedness for subsets of population samples; and it allows estimation of relatedness for a single group or for a single pair of individuals. Individual estimates of relatedness tend to be highly variable but, in aggregate, can still be very useful as data for nonparametric tests. Such tests allow testing for differences in relatedness between two samples or for correlating individual relatedness values with another variable.     

DETECTING CRYPTIC INDIRECT GENETIC EFFECTS

Indirect genetic effects (IGEs) occur when genes expressed in one individual alter the phenotype of an interacting partner. IGEs can dramatically affect the expression and evolution of social traits. However, the interacting phenotype(s) through which they are transmitted are often unknown, or cryptic, and their detection would enhance our ability to accurately predict evolutionary change. To illustrate this challenge and possible solutions to it, we assayed male leg‐tapping behavior using inbred lines of Drosophila melanogaster paired with a common focal male strain. The expression of tapping in focal males was dependent on the genotype of their interacting partner, but this strong IGE was cryptic. Using a multiple‐regression approach, we identified male startle response as a candidate interacting phenotype: the longer it took interacting males to settle after being startled, the less focal males tapped them. A genome‐wide association analysis identified approximately a dozen candidate protein‐coding genes potentially underlying the IGE, of which the most significant was slowpoke. Our methodological framework provides information about candidate phenotypes and candidate single‐nucleotide polymorphisms that underpin a strong yet cryptic IGE. We discuss how this approach can facilitate the detection of cryptic IGEs contributing to unusual evolutionary dynamics in other study systems.     

青杨的遗传分化

分析了10个省市自治区的30个群体的青杨(Populus cathayana Rehd.),共169株,用RAPD方法分析群体间和群体内的DNA多态性。结果显示群体间的DNA多态度远高于群体内的,而且东部群体与西部群体间存在较大的遗传差异,相邻产地之间的遗传差异相对较小。聚类分析结果表明,东、西部群体已出现明显分化。整个聚类图与青杨的地理分布区大致相对应。西部群体内DNA多态性比东部群体高,因此西部群体在研究青杨的起源与演化中将显得更为重要。按照多样性中心与起源中心的关系,青杨可能起源于我国西北部,逐渐向东扩散,形成现代分布格局。