摘要:

AbstractRecent advances in the application of the polymerase chain reaction make it possible to score individuals at a large number of loci. The RAPD (random amplified polymorphic DNA) method is one such technique that has attracted widespread interest. The analysis of population structure with RAPD data is hampered by the lack of complete genotypic information resulting from dominance, since this enhances the sampling variance associated with single loci as well as induces bias in parameter estimation. We present estimators for several population‐genetic parameters (gene and genotype frequencies, within‐ and between‐population heterozygosities, degree of inbreeding and population subdivision, and degree of individual relatedness) along with expressions for their sampling variances. Although completely unbiased estimators do not appear to be possible with RAPDs, several steps are suggested that will insure that the bias in parameter estimates is negligible. To achieve the same degree of statistical power, on the order of 2 to 10 times more individuals need to be sampled per locus when dominant markers are relied upon, as compared to codominant (RFLP, isozyme) markers. Moreover, to avoid bias in parameter estimation, the marker alleles for most of these loci should be in relatively low frequency. Due to the need for pruning loci with low‐frequency null alleles, more loci also need to be sampled with RAPDs than with more conventional markers, and some problems of bias cannot be completely eli

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1994.tb00109.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractHooded sealCystophora cristatatrios consist of an adult female, her pup, and an attending adult male. Using DNA fingerprinting, we excluded the possibility that the attending males within hooded seal trios were the fathers of the pups, proving that these hooded seals did not remain paired from one breeding season to the next. Behavioural observations of the trios after capture and release revealed that male hooded seals displace one another in attending nursing females. Mate guarding appears to be the preferred mating strategy available to male hooded seals given intense competition for females, a very brief nursing period, and oestrus occuring soon after weaning, but its effectiveness remains unclear.

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1994.tb00110.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractKin structure among founders can have a significant effect on subsequent population structure. Here we use the correlation between DNA profile similarity and relatedness calculated from pedigrees to test hypotheses regarding kin structure among founders to the captive Guam rail (Rallus owstoni) population. Five different pedigrees were generated under the following hypotheses: (i) founders are unrelated; (ii) founders are unrelated except for same‐nest chicks; (iii) founders from the same major site are siblings; (iv) founders from the same local site are siblings; and (v) founders are related as defined by a UPGMA cluster analysis of DNA similarity data. Relatedness values from pedigrees 1, 2 and 5 had the highest correlation with DNA similarity but the correlation between relatedness and similarity were not significantly different among pedigrees. Pedigree 5 resulted in the highest correlation overall when using only relatedness values that changed as a result of different founder hypotheses. Thus, founders were assigned relatedness based on pedigree 5 because it had the highest correlations with DNA similarity, was the most conservative approach, and incorporated all field data. The analyses indicated that estimating relatedness using DNA profiles remains problematic, therefore we comparedmean kinship, a measure of genetic importance, withmean DNA profile similarityto determine if genetic importance among individuals could be determined via use of DNA profiles alone. The significant correlation suggests this method may provide more information about population structure than was previously thought. Thus, DNA profiles can provide a reasonable explanation for founder relatedness and mean DNA profile similarity may be helpful in determining relative genetic importance of individuals when detailed pedigrees are absen

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1994.tb00111.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA pseudolysogenic, generalized transducing bacteriophage, UT1, isolated from a natural freshwater habitat, is capable of mediating the transfer of both chromosomal andplasmid DNA between strains ofPseudomonas aeruginosa.Several chromosomal alleles from three differentP. aeruginosastrains were found to transduce at frequencies from 10‐8to 10‐10transductants per PFU at multiplicities of infection (MODbetween 0.1 and 1. Transduction frequencies of certain alleles increased up to 1000‐fold asMOIswere decreased to 0.01. UT1 is also capable of transducing plasmid DNA to indigenous populations of microorganisms in natural lake‐water environments. Data obtained in this study suggest that environmentally endemic bacteriophages such as UT1 are formidable transducers of naturally occurring microbial communities. It should be possible to develop model systems to test transduction in freshwater environments using components derived exclusively from these envir

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1994.tb00112.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractWe have been studying the effects of expression of plasmid‐borne, Tn10‐encoded, tetracycline resistance on the fitness ofEscherichia coliK12. We previously demonstrated large reductions in fitness resulting from induced or constitutive expression of the resistance protein; however, any residual expression by the repressed operon was so slight that possession of an inducible resistance function imposed essentially no burden in the absence of antibiotic. Here, we demonstrate two distinct disadvantages for inducible genotypes relative to isogenic constitutive constructs. During the transition from antibiotic‐free to antibiotic‐containing media, the inducible genotype experiences a longer lag phase prior to growth. In the sustained presence of antibiotic, full induction of the resistance function in the inducible genotype is prevented by the continued action of its repressor. However, these disadvantages may be reduced by increasing the strength of the promoter for the resistance gene in the inducible genotype. Simultaneous consideration of the mode of gene regulation (i.e. constitutive or inducible) and the strength of the resistance‐gene promoter (i.e. maximum level of expression) indicates an adaptive landscape with very strong epistasis and, perhaps, multiple fitn

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1994.tb00113.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractWe report the isolation of a set of hypervariable minisatellite DNA sequences from a blue titParus caeruleusgenomic DNA library. In our strategy, we cloned a minisatellite‐rich DNA fraction into a charomid vector. The resulting cosmid library was screened with the two minisatellite DNA probes 33.6 and 33.15 for recombinants containing a minisatellite DNA insert. A total of 233 positive clones were isolated. Of 37 clones that have been analysed, nine gave polymorphic signals and can be used as single locus probes (SLPs). Four of the SLPs were investigated in more detail. The number of alleles, the heterozygosity and the mutation rate were estimated. Linkage analysis revealed that two of these loci were linked. The SLPs are of value to studies of the mating system and reproductive success in the blue tit, and may also be useful in population genetic studie

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1994.tb00114.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractTransgenic plants that produce pesticidal proteins have the potential to release these products into the environment when the plants are incorporated into soil. This could result in novel exposure of soil organisms to these pesticidal proteins. There is a lack of knowledge about the fate and persistence of transgenic pesticidal products in the soil. A model system of transgenic cotton, which producesBacillus thuringiensis kurstakiδ‐endotoxin (Bt toxin), was used to address this issue. Methods were developed to quantify Btk toxin in soil and soil/plant litter by extraction of the Btk toxin with an aqueous buffer and quantification by ELISA. The highest recovery of Btk toxin from soil was obtained with a high salt, high pH buffer. In addition, for certain soil types, addition of a non‐ionic detergent, Tween‐20, was needed for optimal recovery. Recovery of Btk toxin from soil ranged from 60% for a low clay content, low organic matter soil to 27% for a high clay content, high organic matter soil. The limit of detection of this method is 0.5 ng of extractable toxin per g dry weight soil. The method was shown to be useful in tracking over time the persistence of both purified and transgenic Btk toxin in laboratory exper

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1994.tb00115.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA propiconazole‐resistantTrichoderma harzianumstrain with high phylloplane survival capability was transformed with theE. colihygromycin B phosphotransferase gene (hph), coding for hygromycin B resistance. Four transformants were analysed for survival ability on the phylloplane of tomato plants grown under glasshouse conditions in comparison with their prototype and a yellow, hygromycin B‐sensitive mutant. Over 2 weeks, the four transformants showed higher survival rates in comparison with the wild‐type strain. The yellow mutant TF3/973 did not significantly differ in survival from the transformants. Both hygromycin B resistance and mitotic stability of transformants were evaluated during growthin vitroand after reisolation from tomato phylloplane. Hybridization patterns with the complete plasmid indicated that all four transformants were mitotically stable after several rounds of vegetative growth without selective pressure and during 2 weeks on tomato plants. None of the transformants had lost the ability to grow in the presence of both propiconazole and hygromycin B after growth under the same conditions. The results are discussed in relation to risk assessment of the release of transgenic

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1994.tb00116.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe Pô River basin of northern Italy is the home of distinctive and endemic morphological forms of brown troutSalmo trutta.We used PCR‐direct sequencing and RFLP techniques to study variation in the mitochondrial control region of 225 trout in order to assess genetic relatedness among 18 populations from that region. The distribution analysis of these genotypes among north Italian populations confirmed the phylogenetic differentiation of marbled troutSalmo trutta marmoratuspopulations and the postglacial origin ofS. t. fario.Extensive genetic heterogeneity was observed among morphologically identicalS. t. fariopopulations. Introgression with domestic strains of Atlantic basin origin was detected in all forms. In order to assess the phylogenetic congruence detected in coding and noncoding regions of the mitochondrial genome, we also analysed sequence variation in segments of the cytochromeband ATPase subunit VI genes among representatives of all variants detected in the analysis of the control region. Variation in protein coding genes was only slightly less than that observed in the control region of the same individuals, both in terms of number of variants detected and of pairwise sequence divergence estimates among variants. Phylogenetic analysis based on protein coding genes sequences identified the same phylogenetic groupings defined by the control region analysis and also allowed a partial resolution of their phyletic relationships that was previously unresolved. However, coding and noncoding segments differed substantially in the transition‐transversion ratio (17:0 in coding segments vs. 17:6 in control region segme

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1994.tb00117.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1994.tb00118.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY