排序方式: 共有14条查询结果,搜索用时 31 毫秒
1.
2.
E. F. Legner 《BioControl》1991,36(1):1-18
Estimates of the minimum number of genetic loci governing expressions of gregarious oviposition inMuscidifurax raptorellus Kogan & Legner were enabled by the verification of recombinant males, which were secured from virgin hybrid females, formed
by crossing cohorts from solitary and gregarious populations. Examinations of parasitization behavior in female progeny that
had F1 male fathers indicated the presence of hybrids among the males. Estimates of gene number, made on the basis of variances
in P1, F1, F2 and backcross progeny, and by observing behavior in second and third order backcrosses, ranged from two to 19, with most
between two and five. However, backcrossing data suggested that at least eight loci were actively segregating for this characteristic.
Semi-dominance of the solitary trait (D=0.63 to 0.84), and unequal gene effects probably caused these gene estimated to be
lower than the actual number. Estimates of the coefficient of heritability, in the broad sense based on parental and F1 and F2 variances indicated that variability of gregarious behavior in the experimental environment was influenced >60% by genotypic
factors, offspring-parent regression analyses gave estimates >38%.
相似文献
3.
Carson HL 《Genetica》2002,116(2-3):383-393
Details of female choice of mate in Drosophila silvestris of Hawaii strikingly parallels epigamic behavioral systems in many other animals and may be common in other species of Drosophilidae. Females respond selectively to male circling, wing displays, songs and tactile stimulation with foreleg cilia, a quantitative character that is highly variable in some populations. I hypothesize that the female can exert choice based on these cues from individual males that differ genetically by quantitative trait loci. Laboratory tests show that one third of courting males are repeatedly rejected in favor of a minority of alpha males. This result imposes non-random mating at the local population level. Past multiple-choice lab tests, widely used to measure isolation between pairs of populations or species of Drosophila may be flawed, since random mating has been assumed in the interpretation of results. Pre-mating sexual selection is clearly a powerful intrapopulation force in population biology. This view creates difficulties for discerning any proposed simultaneous interpopulation selective events in the presence of strong female choice. The long-held theory assuming that there is significant selection for pre-mating isolation between groups is questionable. 相似文献
4.
Some kernel traits of agronomical importance in maize are affected by the opaque-2 (o2) gene and background polygenes, which express in different genetic systems such as embryo, endosperm, cytoplasm and maternal
plant. A genetic model for seed quantitative traits with the o2 gene effects and polygenic effects as well as their GE interactions was used for protein content, lysine content, oil content and kernel density in maize. The results suggested
that the o2 gene was involved in the traits investigated but the effects of the o2 gene were distinctive on various traits. The effects of the o2 gene were large on lysine content and protein content while minor on oil content. There was a substantially wide quantitative
variation from polygenes expressing in different genetic systems for the traits evaluated. Significant GE interactions of the o2 gene and background polygenes declared that not only the main effects but also specific expressions depending on environments
were responsible for variation of the traits studied. There seemed to have strong maternal heterosis and slight embryo heterosis
for kernel density. 相似文献
5.
The evolutionary relationship between gene-structure and gene-regulation variation was examined by using data on allozyme
and activity variation for a group of enzyme loci inDrosophila melanogaster. No significant correlation between the two kinds of variation was found, although the present data set is small and probably
not sensitive for tests of association. Various hypotheses of association between the two types of variation are discussed
and it is shown that any association between gene-structure and gene-regulation variation (positive or negative) would be
sensitive to distortion by repeated bottlenecks and genetic drift. Furthermore, random forces would affect gene-structure
(allozyme) variation, which is often controlled by one gene, more severely than enzyme activity variation, which is usually
controlled by many genes. Measurements of activity variation would appear to provide an evolutionarily more stable and reliable
estimate of. loci-specific ‘molecular flexibility’ than measurements of structural variation. It is suggested that locus-specific
gene regulation studies employing a set of major alleles would provide a better test of association between gene-structure
and gene-regulation variation. The relationship between gene regulation and quantitative variation is discussed and a number
of population-genetic questions related to regulatory gene variation are formulated. 相似文献
6.
James F. Crow 《Journal of genetics》2008,87(4):349-353
Although molecular methods, such as QTL mapping, have revealed a number of loci with large effects, it is still likely that
the bulk of quantitative variability is due to multiple factors, each with small effect. Typically, these have a large additive
component. Conventional wisdom argues that selection, natural or artificial, uses up additive variance and thus depletes its
supply. Over time, the variance should be reduced, and at equilibrium be near zero. This is especially expected for fitness
and traits highly correlated with it. Yet, populations typically have a great deal of additive variance, and do not seem to
run out of genetic variability even after many generations of directional selection. Long-term selection experiments show
that populations continue to retain seemingly undiminished additive variance despite large changes in the mean value. I propose
that there are several reasons for this. (i) The environment is continually changing so that what was formerly most fit no
longer is. (ii) There is an input of genetic variance from mutation, and sometimes from migration. (iii) As intermediate-frequency
alleles increase in frequency towards one, producing less variance (as p → 1, p(1 − p) → 0), others that were originally near zero become more common and increase the variance. Thus, a roughly constant variance
is maintained. (iv) There is always selection for fitness and for characters closely related to it. To the extent that the
trait is heritable, later generations inherit a disproportionate number of genes acting additively on the trait, thus increasing
genetic variance. For these reasons a selected population retains its ability to evolve. Of course, genes with large effect
are also important. Conspicuous examples are the small number of loci that changed teosinte to maize, and major phylogenetic
changes in the animal kingdom. The relative importance of these along with duplications, chromosome rearrangements, horizontal
transmission and polyploidy is yet to be determined. It is likely that only a case-by-case analysis will provide the answers.
Despite the difficulties that complex interactions cause for evolution in Mendelian populations, such populations nevertheless
evolve very well. Longlasting species must have evolved mechanisms for coping with such problems. Since such difficulties
do not arise in asexual populations, a comparison of epistatic patterns in closely related sexual and asexual species might
provide some important insights. 相似文献
7.
Konrad Bachmann Kenton L. Chambers H. James Price 《Plant Systematics and Evolution》1984,145(3-4):243-258
CrossingMicroseris pygmaea (10 pappus parts) withM. bigelovii (5 pappus parts) results in hybrids with variable pappus part numbers between 5 and 10. Previous work has shown that a system of four additively acting genes determines the average pappus part numbers of these hybrids. In hybrid B87 two genes have a 10-determining and a 5-determining allele each, two others a 5-determining and a null (inactive or missing) allele. Genetic linkage of one of the latter with the enzyme geneEsterase-1 and the leaf shape genespatulate leaves has been demonstrated. Here we demonstrate linkage between one of the two 10-determining genes and the enzyme locusEsterase- Y/B. The genotypes in the pappus part system of many specimens can now be fully determined. This is a major advance for the analysis of the evolution of this additive polygenic system.Genetics of Pappus Part Numbers inMicroseris Hybrid B87, II.—Part I:Bachmann & al. 1981. 相似文献
8.
水稻单株有效穗数主基因+多基因混合遗传分析 总被引:1,自引:0,他引:1
选择单株有效穗数差异大的3个亲本CB1(15.3)、CB4(6.4)和CB7(11.8),配制CB1×CB4和CB7×CB4组合,建立了相应的P_1、F_1、P_2、B_1、B_2、F_2群体,将其分为中、晚两个生产季节种植,考察了有效穗数性状.利用主基因+多基因混合遗传模型理论的Akaike信息准则(AIC)在B_1、B_2、F_2代中鉴定影响数量性状的主基因存在与否,主基因存在时通过分离分析估计主基因和微效基因的遗传效应及所占总变异的分量.结果表明该性状在所有B_1、B_2、F_2中均符合2对加性-显性-上位性主基因+加性-显性-上位性多基因的遗传模式,主基因遗传率为30.64%-72.26%,多基因遗传率为3.41%-28.20%,总基因遗传率为45.96%-87.29%;相同组合种植季别主基因遗传率及一阶参数对比表明,杂交亲本的选择及种植季别对该性状遗传率影响较小,h_a、h_b、j_(ab)、j_(ba)值均为负值表明显性效应和加性显性互作对该性状表达具有抑制作用. 相似文献
9.
10.
Ghost quantitative trait loci (QTL) are the false discoveries in QTL mapping, that arise due to the “accumulation” of the polygenic effects, uniformly distributed over the genome. The locations on the chromosome that are strongly correlated with the total of the polygenic effects depend on a specific sample correlation structure determined by the genotypes at all loci. The problem is particularly severe when the same genotypes are used to study multiple QTL, e.g. using recombinant inbred lines or studying the expression QTL. In this case, the ghost QTL phenomenon can lead to false hotspots, where multiple QTL show apparent linkage to the same locus. We illustrate the problem using the classic backcross design and suggest that it can be solved by the application of the extended mixed effect model, where the random effects are allowed to have a nonzero mean. We provide formulas for estimating the thresholds for the corresponding t-test statistics and use them in the stepwise selection strategy, which allows for a simultaneous detection of several QTL. Extensive simulation studies illustrate that our approach eliminates ghost QTL/false hotspots, while preserving a high power of true QTL detection. 相似文献