排序方式: 共有21条查询结果,搜索用时 31 毫秒
1.
Diallel analysis for sex-linked and maternal effects 总被引:40,自引:0,他引:40
J. Zhu B. S. Weir 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1996,92(1):1-9
Genetic models including sex-linked and maternal effects as well as autosomal gene effects are described. Monte Carlo simulations were conducted to compare efficiencies of estimation by minimum norm quadratic unbiased estimation (MINQUE) and restricted maximum likelihood (REML) methods. MINQUE(1), which has 1 for all prior values, has a similar efficiency to MINQUE(), which requires prior estimates of parameter values. MINQUE(1) has the advantage over REML of unbiased estimation and convenient computation. An adjusted unbiased prediction (AUP) method is developed for predicting random genetic effects. AUP is desirable for its easy computation and unbiasedness of both mean and variance of predictors. The jackknife procedure is appropriate for estimating the sampling variances of estimated variances (or covariances) and of predicted genetic effects. A t-test based on jackknife variances is applicable for detecting significance of variation. Worked examples from mice and silkworm data are given in order to demonstrate variance and covariance estimation and genetic effect prediction. 相似文献
2.
G. P. Gill C. F. Harvey R. C. Gardner L. G. Fraser 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(3):439-445
Two sex-linked random amplified polymorphic DNA (RAPD) markers identified from Actinidia chinensis were converted into sequence-characterised amplified regions (SCARs) for the large-scale screening of Actinidia breeding populations. Initial SCAR primers converted one RAPD (SmX) into a dominant marker, but the other (SmY), which was
potentially more useful because of its linkage to the male determining ‘Y’ locus, failed to retain polymorphism. This difficulty
was overcome by cloning and sequencing the alternate ‘allele’ from female plants, and then designing ‘allele’-specific primers
that utilised nucleotide differences between the sexes. Using a quick squash-blot method of DNA extraction, the SCAR primers
were tested in 120 A. chinensis plants to determine their gender. The system is now in use for large-scale screening of seedling populations in the Actinidia breeding programme. The sex-linked SCAR primers also functioned with plants from some other geographically separate accessions
of A. chinensis and with plants in the closely related polyploid species A. deliciosa, but did not amplify a sex-linked band in more distantly related species of Actinidia.
Received: 27 December 1997 / Accepted: 5 March 1998 相似文献
3.
Armando Vega-Lpez Marcela Galar-Martínez Fausto Alejandro Jimnez-Orozco Ethel García-Latorre Maria Lilia Domínguez-Lpez 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2007,146(4):672
Polychlorinated biphenyls (PCBs) are persistent xenobiotics within aquatic environments, which elicit diverse toxic effects such as induction of oxidative stress. Despite numerous earlier studies, no detailed information exists on the toxic response by different sexes in fish. The aim of this study was to determine sex-linked differences in oxidative stress response and antioxidant defenses in Girardinichthys viviparus, an endangered fish endemic to Mexico, when exposed to sub-lethal concentrations of waterborne PCBs. The biological markers evaluated were lipid peroxidation (LPOX), superoxide dismutase (SOD) and catalase (CAT) activity. Adult eight-month-old specimens born in the laboratory were exposed to ½ of the LC0 (0.92 mg PCBs/L) in semi-hard synthetic water and sacrificed on days 1, 2, 4, 8 and 16 for biomarker assays. Sex-linked differences were observed in the control fish with respect to all three factors assayed. PCBs elicited significant (p < 0.01) time- and sex-dependent LPOX levels which were higher in the case of males. In PCB-treated G. viviparus, SOD activity was depressed in both sexes and appears to return to pre-exposure levels after 16 days in males only. In contrast, CAT was significantly induced (p < 0.01) in both sexes. This enzyme may be responsible for balancing oxidative stress and antioxidant defenses under experimental conditions. PCBs at sub-lethal concentrations are hazardous to both sexes of G. viviparus since these compounds are able to induce liver LPOX and changes in the antioxidant defense activities. The relationship between these biomarkers and cytochrome P450 and CYP1A induction is also discussed. 相似文献
4.
N Blavet H Blavet A Muyle J K?fer R Cegan C Deschamps N Zemp S Mousset S Aubourg R Bergero D Charlesworth R Hobza A Widmer GAB Marais 《BMC genomics》2015,16(1)
Background
Silene latifolia represents one of the best-studied plant sex chromosome systems. A new approach using RNA-seq data has recently identified hundreds of new sex-linked genes in this species. However, this approach is expected to miss genes that are either not expressed or are expressed at low levels in the tissue(s) used for RNA-seq. Therefore other independent approaches are needed to discover such sex-linked genes.Results
Here we used 10 well-characterized S. latifolia sex-linked genes and their homologs in Silene vulgaris, a species without sex chromosomes, to screen BAC libraries of both species. We isolated and sequenced 4 Mb of BAC clones of S. latifolia X and Y and S. vulgaris genomic regions, which yielded 59 new sex-linked genes (with S. vulgaris homologs for some of them). We assembled sequences that we believe represent the tip of the Xq arm. These sequences are clearly not pseudoautosomal, so we infer that the S. latifolia X has a single pseudoautosomal region (PAR) on the Xp arm. The estimated mean gene density in X BACs is 2.2 times lower than that in S. vulgaris BACs, agreeing with the genome size difference between these species. Gene density was estimated to be extremely low in the Y BAC clones. We compared our BAC-located genes with the sex-linked genes identified in previous RNA-seq studies, and found that about half of them (those with low expression in flower buds) were not identified as sex-linked in previous RNA-seq studies. We compiled a set of ~70 validated X/Y genes and X-hemizygous genes (without Y copies) from the literature, and used these genes to show that X-hemizygous genes have a higher probability of being undetected by the RNA-seq approach, compared with X/Y genes; we used this to estimate that about 30 % of our BAC-located genes must be X-hemizygous. The estimate is similar when we use BAC-located genes that have S. vulgaris homologs, which excludes genes that were gained by the X chromosome.Conclusions
Our BAC sequencing identified 59 new sex-linked genes, and our analysis of these BAC-located genes, in combination with RNA-seq data suggests that gene losses from the S. latifolia Y chromosome could be as high as 30 %, higher than previous estimates of 10-20 %.Electronic supplementary material
The online version of this article (doi:10.1186/s12864-015-1698-7) contains supplementary material, which is available to authorized users. 相似文献5.
Accurate identification of sex in birds is important for the management and conservation of avian wildlife in several ways, namely in the development of population, behavioral and ecological studies, as well as in the improvement of ex situ captive breeding programs. In general, nestlings, juveniles and adult birds of a wide number of sexually monomorphic species cannot be sexed based on phenotypic traits. The development of molecular methodologies for avian sexing overcame these difficulties, allowing a reliable gender differentiation for these species. The polymerase chain reaction (PCR)-based methods have been widely applied in molecular sexing of birds, using a large diversity of sex-linked markers. During the last 15 yrs, there was a continuous improvement in the PCR-based protocols for bird sexing, increasing the accuracy, speed and high-throughput applicability of these techniques. The recent advances in real-time PCR platforms and whole genome analysis methods provided new resources for the detection and analysis of novel specific markers and protocols. This review presents a comparative guide of classical and recent advances in PCR-based methods for avian molecular sexing, highlighting its strengths and limitations. Future research opportunities in this field are also addressed. 相似文献
6.
7.
8.
This paper presents results of the genetic and cytological analysis of 144 sex-linked recessive lethals, plus 1 non-lethal. All of them were induced by I−R hybrid dysgenesis. This collection of mutants was pooled from experiments involving inducer chromosomes that differ in the chrosomal position of their I elements. Our results show that 30% of the recessive lethals are associated with chromosomal rearrangements which depend on the strength of the I−R interaction. These lethals are induced on both inducer- and reactive-origin chromosomes, and their frequency is dependent on the structure of the inducer chromosome used. The I−R-induced lethals occur along the entire length of the X chromosome. These sites probably correspond to specific loci which are more or less homologous with I. The complementation relationshups showed that some specific loci were more frequently involved in all the lethal mutations tested. The most sensitive loci are, in order of observation: l(1)J1, ct, f, ma1 and m. Among induced recessive lethals considered to be point mutation, complementation tests showed that many of them are in fact multilocius deficiencies which can be detected only at the molecular level.
It seems that the production of I−R rearrangements (cytologically visible or not) may be the most important mechanism leading to lethal mutations. These mutations probably occur during the transposition of I elements, hence their importance from an evolutionary standpoint. 相似文献
9.
Lawrence C. Shimmin Benny Hung-Junn Chang David Hewett-Emmett Wen-Hsiung Li 《Journal of molecular evolution》1993,37(2):160-166
It is commonly believed that the rate of mutation is much higher in males than in females because the number of germ-cell
divisions per generation is much larger in males than in females. However, the precise magnitude of the male-to-female mutation
rate ratio (α
m
) remains unknown. Recently there have been efforts to estimate α
m
by using DNA sequence data from different species. We have studied the potential problems in such an approach. We found that
the rate of synonymous substitution varies about fivefold among X-linked genes, as large as the variation among autosomal
genes. This large variation makes the assumption of selective neutrality of synonymous changes dubious, so one should be cautious
in using the synonymous rates in X-linked and autosomal genes to estimate α
m
. A similar difficulty was also observed in using nonhomologous intron sequences to estimate α
m
. Contrary to the expectation that X-linked sequences should evolve more slowly than autosomal sequences, theAlu repeat in the last intron of the X-linked zinc finger gene has evolved faster than the four autosomalAlu repeats used in this study. It appears that the best way to estimate α
m
is to use homologous sequences. However, such sequences may be involved in gene conversion events. In fact, we found evidence
that the Y-linked and X-linked zinc finger genes have been involved in multiple conversion events during primate evolution.
Thus, the possibility of gene conversion should be considered when using homologous sequences to estimate α
m
.
Presented at the NATO Advanced Research Workshop onGenome Organization and Evolution, Spetsai, Greece, 16–22 September 1992 相似文献
10.
INTRODUCTIONInanimalbrce(lingexperilllents,sex--linkedandmaternaleff(3ctsaretheprimarysourcesofreciprocaleffects.Eiap1etal.(1966)presentedamodelcontainillgparametersforsex--linlcedan(lmaternaleffectsasxvellasautosomalgeneticeffects.Cockerhalllandacid(1977… 相似文献