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PubMed2001

Additional evidence that genetic variation of MAO-A gene supports a gender subtype in obsessive-compulsive disorder.

Studies have recently reported a sexually dimorphic association between obsessive-compulsive disorder (OCD) and a polymorphism related with variations in MAO-A activity. These observations suggest the possibility of gender differences in genetic susceptibility for OCD. We thus reexamined the MAO-A/EcoRV polymorphism in a sample of 122 OCD patients and 124 healthy subjects. An excess of allele 1 in OCD females with major depression disorder was confirmed as previously reported. This difference was more strongly associated with OCD females than males in the total sample. Finally, we analyzed a sample of 51 OCD trios. Haplotype-based haplotype relative risk (HHRR) analysis of the inheritance of the MAO-A variants revealed in the female probands that 14 out of 19 transmitted the allele 1, providing significant evidence for an allelic association between OCD and MAO-A gene. In conclusion, our findings may provide molecular evidence to identify a clinically meaningful gender subtype. However, an effort should be made to replicate the analysis in larger samples of informative parents using strategies such as transmission disequilibrium test to allow definite conclusions.

Adult↗
PubMed2002

[Genetic variation of main restorer lines of hybrid rice in China was revealed by microsatellite markers].

A total of thirty-five restorer lines of hybrid rice (Oryza sativa L.) were analyzed by twenty-five SSR (simple sequence repeats) primer pairs, which disperse on 12 chromosomes in rice. Those primers detected 65 alleles among 35 restorer lines of hybrid rice. Per primer pair detected 2.6 alleles on the average. PIC (polymorphism index content) values ranged from 0.206 to 0.682. PIC value is 0.414 on the average. The result from cluster analysis shows that hybrid rice restorer lines have abundant resource in China, but the genetic diversity is small and the genetic background is vulnerable among them. The utilization of rice heterosis was limited seriously.

Genetic Variation↗
PubMed2004

Contrasting patterns of quantitative and neutral genetic variation in locally adapted populations of the natterjack toad, Bufo calamita.

The relative importance of natural selection and genetic drift in determining patterns of phenotypic diversity observed in nature is still unclear. The natterjack toad (Bufo calamita) is one of a few amphibian species capable of breeding in saline ponds, even though water salinity represents a considerable stress for them. Results from two common-garden experiments showed a pattern of geographic variation in embryonic salinity tolerance among populations from either fresh or brackish environments, consistent with the hypothesis of local adaptation. Full-sib analysis showed increased variation in survival among sibships within population for all populations as osmotic stress was increased (broad-sense heritability increased as salinity raised). Nevertheless, toads native to the brackish water environment had the highest overall survival under brackish conditions. Levels of population genetic differentiation for salinity tolerance were higher than those of neutral genetic differentiation, the latter obtained through the analysis of eight microsatellite loci. Microsatellite markers also revealed little population differentiation, lack of an isolation-by-distance pattern, and moderate gene flow connecting the populations. Therefore, environmental stress tolerance appears to have evolved in absence of geographic isolation, and consequently we reject the null hypothesis of neutral differentiation.

Adaptation, Physiological↗
PubMed2001

Assessment of genetic variation and differentiation of hop genotypes by microsatellite and AFLP markers.

Microsatellites have many desirable marker properties and have been increasingly used in crop plants in genetic diversity studies. Here we report on the characterisation of microsatellite markers and on their use for the determination of genetic identities and the assessment of genetic variability among accessions from a germplasm collection of hop. Thirty-two polymorphic alleles were found in the 55 diploid genotypes, with an average number of eight alleles (3.4 effective alleles) for four microsatellite loci. Calculated polymorphic information content values classified three loci as informative markers and two loci as suitable for mapping. The average observed heterozygosity was 0.7 and the common probability of identical genotypes was 3.271 x 10(-4). An additional locus, amplified by one primer pair, was confirmed by segregation analysis of two crosses. The locus discovered was heterozygous, with a null allele in the segregating population. The same range of alleles was detected in nine triploid and five tetraploid hop genotypes. Cultivar heterozygosity varied among all 69 accessions, with only one cultivar being homozygous at four loci. Microsatellite allele polymorphisms distinguished 81% of all genotypes; the same allelic profile was found mainly in clonally selected cultivars. Cultivar-specific alleles were found in some genotypes, as well as a specific distribution of alleles in geographically distinct hop germplasms. The genetic relationship among 41 hop accessions was compared on the basis of microsatellite and AFLP polymorphisms. Genetic similarity dendrograms showed low correlation between the two marker systems. The microsatellite dendrogram grouped genetically related accessions reasonably well, while the AFLP dendrogram showed good clustering of closely related accessions and, additionally, separated two geographically distinct hop germplasms. The results of microsatellite and AFLP analysis are discussed from the point of view of the applicability of the two marker systems for different aspects of germplasm evaluation.

Alleles↗
PubMed2002

Tryptophan hydroxylase immunoreactivity is altered by the genetic variation in postmortem brain samples of both suicide victims and controls.

Several lines of evidence suggest that a partly genetically controlled serotonergic dysfunction is involved in the biological pathogenesis of suicide. In this study, we measured tryptophan hydroxylase (TPH) immunoreactivity as a pre-synaptic marker, and serotonin receptor 2A (5HT2A receptor) density as a post-synaptic marker in the serotonergic system in 10 postmortem brains of suicide victims. We also examined whether TPH gene polymorphisms (A218C and A-6526G polymorphisms) could affect TPH immunoreactivity and 5HT2A receptor gene polymorphism (A-1438G polymorphism) could affect 5HT2A receptor density in 28 postmortem brain samples. No significant differences were found in TPH immunoreactivity or 5HT2A receptor density between suicide victims and controls. The AA genotype of the A218C polymorphism of the TPH gene showed higher TPH immunoreactivity along with lower 5HT2A receptor density than did any other genotypes in the postmortem brains of both suicide victims and controls. Our findings suggest that the A218C polymorphism of the TPH gene can be expected to provide new insights not only for neurobiological studies of suicide, but also for research into the behavioral characteristics that may be associated with serotonergic dysfunction.

Genetic Variation↗
PubMed1999

Molecular analysis of the genetic variation among penicillin-susceptible and penicillin-resistant Streptococcus pneumoniae serotypes in Canada.

Few studies have examined the genetic relatedness within and between serotypes of Streptococcus pneumoniae. Penicillin-susceptible S. pneumoniae (PSSP) isolates (n=170) and penicillin-resistant S. pneumoniae (PRSP) isolates (n=48) belonging to 13 different serotypes from across Canada were studied to further understand the molecular epidemiology of S. pneumoniae. PRSP of serotypes 6B, 14, and 19F appeared to be novel clones, differentiated by pulsed-field gel electrophoresis from the recognized international penicillin-resistant clones belonging to these serotypes. In addition, not all PRSP strains shared similar genetic backgrounds with PSSP strains of the same serotype, suggesting that in Canada, certain PRSP strains have emerged from new unique lineages of PRSP. Although there was significant heterogeneity among S. pneumoniae of different serotypes, certain serotypes (3, 7F, and 22F) appeared to be more clonally related despite having originated from different geographic regions.

Cluster Analysis↗
PubMed2005

A first assessment of genetic variation among Morchella esculenta (morel) populations.

Habitat loss and fragmentation have serious consequences for species diversity as well as genetic diversity within a species. As the most sought-after culinary fungus in the Midwest United States, morels (Morchella esculenta and related species) demand the attention of conservationists interested in preserving biological and genetic diversity. Little is known about the natural history of M. esculenta, which is critical information for understanding population dynamics as well as the impacts of habitat fragmentation and harvesting. We report initial results from our long-term studies of genetic variability among fruiting bodies at the Conard Environmental Research Area at Grinnell College, Grinnell, Iowa. Using random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR), a technique that has been successfully used to examine intrapopulation structure and detect clonal populations in numerous fungi, we found substantially higher levels of genetic polymorphism among 57 fruiting bodies than has been previously reported. Though laboratory studies indicate that the inbreeding potential for this fungus is high, we found little evidence for inbreeding, with only two pairs of the randomly chosen isolates having identical genotypes at the 34 loci examined. This work highlights the importance of further attempts to resolve important aspects of the morel life cycle regarding heterokaryosis and inbreeding potential.

Ascomycota↗
PubMed2006

Genetic variation of farrowing kinetics traits and their relationships with litter size and perinatal mortality in French Large White sows.

Genetic parameters of litter traits and their relationships with farrowing kinetics traits were estimated in a Large White population to examine the impact of selection for litter size on perinatal mortality and one of its main determinants, farrowing kinetics. Data were collected on 2,947 farrowings from 1,267 sows between 1996 and 2004. Litter traits included the number born in total (NBT), number born alive (NBA), and the number (NSB) and proportion (PSB) of stillborn piglets. Four farrowing kinetics traits were considered: farrowing duration (FD), birth interval (BI = FD/NBT), heterogeneity of birth intervals (SDNB = SD of the number of piglets born each one-half hour), and birth assistance (BA) during the farrowing process. Genetic parameters were estimated using restricted maximum likelihood methodology. All traits were analyzed using a mixed linear animal model including year x month and parity as fixed effects; the additive genetic value of each animal and the sow permanent environment were treated as random effects. To normalize their distribution, kinetics traits were Box-Cox-transformed. Low heritability estimates were obtained for litter size and mortality traits, which was in agreement with literature results (i.e., 0.10 +/- 0.02, 0.08 +/- 0.02, 0.19 +/- 0.02, and 0.14 +/- 0.02 for NBT, NBA, NSB, and PSB, respectively). Heritability values were also low for kinetics traits: 0.10 +/- 0.02, 0.08 +/- 0.02, 0.01 +/- 0.01, and 0.05 +/- 0.03 for FD, BI, SDNB, and BA, respectively. The genetic correlation between NBT and NBA was strongly positive (ra = 0.90). On both phenotypic and genetic scales, NBT was positively associated with stillbirth (ra = 0.45 +/- 0.11, rp = 0.38 for NSB; ra = 0.46 +/- 0.13, rp = 0.17 for PSB). Conversely, NBA had low correlations with SB and PSB. Number born in total was moderately correlated to FD (ra = 0.34 +/- 0.15) and BI (ra = -0.37 +/- 0.15). A stronger relationship was found between NBA and BI (ra = -0.49 +/- 0.13), whereas the relationship with FD was lower (ra = 0.16 +/- 0.17). Moreover, FD was strongly correlated with stillbirth (ra = 0.42 +/- 0.12 with NSB), whereas BI was nearly independent of stillbirth. Contrary to selection on NBT, selection on NBA appears to be a good way to limit the negative side effects on stillbirth. Moreover, selection on NBA would lead to a small increase in FD and a faster and more regular birth process than would be obtained by selecting on NBT.

Animals↗
PubMed1984

Pleiotropic overdominance and the maintenance of genetic variation in polygenic characters.

A model of selection is described in which optimizing phenotypic selection is combined with pleiotropic overdominance. Thus, the role that mutation commonly plays in models of phenotypic evolution is replaced by balancing selection. Expressions are provided for the equilibrium genetic variance in phenotype and for the heterozygosity. An approximate analysis of the transient properties of the model shows that, in certain circumstances, the behavior is quite similar to that of models based on the interaction of mutation and selection.

Genes, Dominant↗
PubMed1991

Antigenic and genetic variation in cytopathic hepatitis A virus variants arising during persistent infection: evidence for genetic recombination.

Variants of hepatitis A virus (pHM175 virus) recovered from persistently infected green monkey kidney (BS-C-1) cells induced a cytopathic effect during serial passage in BS-C-1 or fetal rhesus kidney (FRhK-4) cells. Epitope-specific radioimmunofocus assays showed that this virus comprised two virion populations, one with altered antigenicity including neutralization resistance to monoclonal antibody K24F2, and the other with normal antigenic characteristics. Replication of the antigenic variant was favored over that of virus with the normal antigenic phenotype during persistent infection, while virus with the normal antigenic phenotype was selected during serial passage. Viruses of each type were clonally isolated; both were cytopathic in cell cultures and displayed a rapid replication phenotype when compared with the noncytopathic passage 16 (p16) HM175 virus which was used to establish the original persistent infection. The two cytopathic virus clones contained 31 and 34 nucleotide changes from the sequence of p16 HM175. Both shared a common 5' sequence (bases 30 to 1677), as well as sequence identity in the P2-P3 region (bases 3249 to 5303 and 6462 to 6781) and 3' terminus (bases 7272 to 7478). VP3, VP1, and 3Cpro contained different mutations in the two virus clones, with amino acid substitutions at residues 70 of VP3 and 197 and 276 of VP1 of the antigenic variant. These capsid mutations did not affect virion thermal stability. A comparison of the nearly complete genomic sequences of three clonally isolated cytopathic variants was suggestive of genetic recombination between these viruses during persistent infection and indicated that mutations in both 5' and 3' nontranslated regions and in the nonstructural proteins 2A, 2B, 2C, 3A, and 3Dpol may be related to the cytopathic phenotype.

Animals↗
PubMed2003

Contrasting patterns of genetic variation in the two sympatric geckos Gekko tawaensis and G. japonicus (Reptilia: Squamata) from western Japan, as revealed by allozyme analyses.

Allozyme variation in two congeneric sympatric geckos, Gekko tawaensis and G. japonicus, from western Japan was examined. These species show similar densities and spatial arrangements of populations in this region, and their genetic structures are thus expected to have been formed under the influences of comparable geohistorical, environmental, and demographic factors. Results of the analyses, however, revealed strikingly different genetic patterns in the two species. Populations of G. tawaensis invariably showed a remarkably lowered heterozygosity (0-0.017) compared to G. japonicus (0.089-0.124). On the other hand, the genetic heterogeneity among populations is much greater in G. tawaensis (F(ST)=0.726) than in G. japonicus (F(ST)=0.101). The Mantel test failed to detect any significant correlations between log (estimated migration rate) and log (geographic distance) in either species, or between matrices of interpopulation pairwise F(ST) for the two species. These results suggest that, in each species, formation of the current genetic structure in western Japan has been chiefly influenced by stochastic factors, rather than the geohistorical architecture of this region. The high F(ST) and low heterozygosity in G. tawaensis suggest the effects of severe local fragmentation. On the other hand, the relatively low F(ST) and high heterozygosity in G. japonicus imply extensive gene flow among populations. Absence of significant correlations between the estimated migration rate and geographic distance in G. japonicus may suggest that such gene flow is promoted by human-mediated transport of this primarily house-dwelling lizard.

Animals↗