Resumo em Inglês:

Genomic disorders refer to a group of syndromes caused by DNA rearrangements, such as deletions and duplications, which result in an alteration of normal gene dosage. The chromosomal rearrangements are usually relatively small and often difficult to detect cytogenetically. In a subset of such conditions the rearrangements comprise multiple unrelated contiguous genes that are physically linked and thus have been referred to as contiguous gene syndromes (CGS). In general, each syndrome presents a complex clinical phenotype that has been attributed generally to dosage sensitive gene(s) present in the responsible chromosomal interval. A common mechanism for CGS resulting from interstitial deletion/duplication has recently been elucidated. The DNA rearrangements result from nonallelic homologous recombination (NAHR) utilizing flanking low-copy repeats (LCRs) as recombination substrates. The resulting rearrangements often involve the same genomic region, a common deletion or duplication, making it difficult to assign a specific phenotype or endophenotype to a single responsible gene. The human and mouse genome sequencing projects, in conjunction with the ability to engineer mouse chromosome rearrangements, have enabled the production of mouse models for CGS and genomic disorders. In this review we present an overview of different techniques utilized to generate mouse models for selected genomic disorders. These models foment novel insights into the specific genes that convey the phenotype by dosage and/or position effects and provide opportunities to explore therapeutic options.

Resumo em Inglês:

This study reports the frequencies of the CCR5D32 mutation of the beta-chemokine 5 gene and discusses the possible effects of past and recent gene flow in three quilombo remnants (Brazilians communities with anthropological African ancestry whose ancestors were escaped slaves): Rio das Rãs, Mocambo, and São Gonçalo in the northeastern region of Brazil. The CCR5D32 allele frequency of the Mocambo population was significantly higher (5.6%) than that found in the Rio das Rãs (1%) and São Gonçalo (0.9%) populations. These differences may reflect different proportions of parental populations in the founders individuals, a founder-effect and/or different histories of inter-ethnic contact. The frequency of the CCR5D32 allele in the Mocambo sample is similar to that found in those urban Brazilian populations which have a large amount of European genetic input, indicating a European contribution to the gene pool of this population and suggesting that, perhaps since its foundation, Mocambo has had a high level of admixture or experienced a founder-effect.

Resumo em Inglês:

Neurofibromatosis type 1 (NF1) is a common autosomal dominant disorder caused by mutations in the NF1 gene. In the present study, a total of 55 unrelated NF1 patients were screened for mutations in the GAP-related domain/GRD (exons 20-27a) by single-strand conformation polymorphism (SSCP). Four different mutations were identified and, taken together, they comprise one nonsense substitution (Q1189X), one deletion (3525-3526delAA), one missense substitution (E1356G) and one mutation in the splice acceptor site (c.4111-1G>A). One novel polymorphism (c.4514+11C>G) and other three putative polymorphisms were also found (c.3315-27G>A, V1146I and V1317A). Genotype-phenotype correlations were investigated, but no particular association was detected.

Resumo em Inglês:

Specific Apolipoprotein E (ApoE) genotypes are thought to be associated with risk for Alzheimer's disease (AD). It is essential to understand how this genetic factor affects cognitive decline and dementia in the general population. One hundred and fifty elderly persons residing at social nursing centers in different provinces of Saudi Arabia were tested for ApoE genotypes, using PCR amplification of genomic DNA followed by DNA digestion with Cfo I. All subjects were diagnosed with regard to cognitive decline and dementia. In the general Saudi population, the ApoE4 allele was found to be a weaker predictor for dementia than for AD. This may be a result of non-AD pathological processes and/or of most prevalent dementia at an age when the ApoE4 effect on the AD/dementia risk has decreased.

Resumo em Inglês:

We investigated the polymorphic tetranucleotide repeat (TTTA)n located in the fourth intron of the CYP19 gene in two Brazilian populations. The frequencies of the five common alleles (A) in Euro- and Afro-Brazilians were, respectively: seven repeats (A5), 0.586 and 0.80; eight repeats (A4), 0.092 and 0.06; nine repeats (A3), 0.014 and 0.01; eleven repeats (A2), 0.284 and 0.09; twelve repeats (A1), 0.021 and 0.04. In addition, one Euro-Brazilian individual had a rare allele with 13 repeats. The allelic frequencies in Euro- and Afro-Brazilians differed statistically (p < 10-3). The two samples were found to be in Hardy-Weinberg equilibrium (p = 0,828 and p = 0,995).

Resumo em Inglês:

Mutations in the KAL-1 gene localized at Xp22.3 have been shown to be responsible for the X-linked Kallmann syndrome (KS), a disorder characterized by the association of hypogonadotropic hypogonadism and anosmia. In this paper, we describe the investigation of two families with X-linked KS, in which similar interstitial deletions ning exons 5 to 10 of the KAL-1 gene were identified. The presence of interspersed repetitive DNA sequences within the KAL-1 gene might have predisposed to this type of mutation.

Resumo em Inglês:

In the present study, the coding region of the H gene was sequenced and analyzed in fourteen genera of New World primates (Alouatta, Aotus, Ateles, Brachyteles, Cacajao, Callicebus, Callithrix, Cebus, Chiropotes, Lagothrix, Leontopithecus, Pithecia, Saguinus, and Saimiri), in order to investigate the evolution of the gene. The analyses revealed that this coding region contains 1,101 nucleotides, with the exception of Brachyteles, the callitrichines (Callithrix, Leontopithecus, and Saguinus) and one species of Callicebus (moloch), in which one codon was deleted. In the primates studied, the high GC content (63%), the nonrandom distribution of codons and the low evolution rate of the gene (0.513 substitutions/site/MA in the order Primates) suggest the action of a purifying type of selective pressure, confirmed by the Z-test. Our analyses did not identify mutations equivalent to those responsible for the H-deficient phenotypes found in humans, nor any other alteration that might explain the lack of expression of the gene in the erythrocytes of Neotropical monkeys. The phylogenetic trees obtained for the H gene and the distance matrix data suggest the occurrence of divergent evolution in the primates.

Resumo em Inglês:

In the present study, 20 species of Siluriformes fish were analyzed in order to determine their nuclear DNA content and compare these data with their diploid number. In addition, the extension and importance of the changes that occurred during the process of diversification in the group of Neotropical freshwater catfish were investigated. The only species studied of the family Doradidae, Rhinodoras d'orbignyi (2n = 58), presented 3.46 ± 0.13 pg of DNA. Among the species of the family Heptapteridae, the values of nuclear DNA content and the diploid numbers ranged from 1.13 ± 0.09 pg of DNA in Pimelodella sp. (2n = 46) to 2.38 ± 0.07 pg of DNA in Imparfinis mirini (2n = 58). The family Loricariidae showed the widest variation in diploid number and nuclear DNA content values, ranging from 2n = 52 and 3.96 ± 0.22 pg of DNA in Liposarcus anisitsi to 2n = 76 and 4.90 ± 0.12 pg of DNA in Hypostomus sp. 4. In this group, two local samples of Pimelodus maculatus (Pimelodidae) were analyzed, and both exhibited 2n = 56, but different nuclear DNA content values (2.68 ± 0.22 pg and 2.82 ± 0.20 pg, respectively). Among the Pseudopimelodidae species analyzed, Pseudopimelodus mangurus (2n = 54) showed 2.23 ± 0.15 pg and Microglanis cottoides (2n = 54) exhibited 2.50 ± 0.18 pg of DNA. Two species of Trichomycterus (Trichomycteridae) also presented the same diploid number, 2n = 54 chromosomes, but, while the species from the Quinta stream presented a DNA content of 2.62 ± 0.19 pg, in the sample from the Capivara river this value was 2.30 ± 0.23 pg. In the analyzed species, the results showed that the changes in DNA content were frequently not followed by changes in the diploid number. This fact permits to suggest that, in addition to structural chromosome rearrangements, other mechanisms, including deletions, duplications and polyploidy, could be involved in the process of species differentiation in the representatives of the fish order Siluriformes.

Resumo em Inglês:

In this study, the RAPD technique was used to analyze the genetic structure of populations of the fish Astyanax altiparanae (Characidae, Tetragonopterinae) living in the lower, middle and upper Paranapanema River, Brazil. The aim was to assess this structure regarding fish handling and conservation programs. The genetic variability (P) was found to be 42.64%, 75% and 75% in the low, middle and upper reaches, respectively. The dendrogram of genetic similarity, obtained by comparative analysis of the sets of samples from the three sites, showed the formation of three clusters. All of the genetic parameters used indicate that the population in the lower Paranapanema is genetically different from those in the middle and upper sections. The theta P test shows that the low Paranapanema is highly differentiated from the middle (0.2813) and upper (0.2912) Paranapanema, while the differentiation between the last two is moderate (0.0895). The data obtained in the present work suggest that recolonization and conservation studies should not be focused on the species A. altiparanae as such, but on the conservation units, because they are the genetically differentiated populations.

Resumo em Inglês:

In this paper, we provide a cytogenetic analysis of Eleutherodactylus guentheri, E. parvus and E. binotatus. All of the species had a diploid chromosomal number of 2n = 22. The karyotypes of E. guentheri and E. parvus were very similar and differed only slightly in the morphology of pair 2. These two species also had an NOR-bearing secondary constriction on the long arms of pair 6. The karyotype of E. binotatus differed from those of E. guentheri and E. parvus in the morphology and size of the chromosomes, in the number of chromosomal arms, in the NOR location (detected on the short arms of pair 1), and in the pattern of heterochromatin. These results reinforce the differences between E. guentheri and E. binotatus and support the existence of two species group. Five individuals of E. binotatus showed morphs for pairs 2 and 3. These morphs probably arose from the translocation of a segment from one chromosome of pair 3 to a homologue of pair 2. In addition, some mitotic metaphases of E. binotatus showed spontaneous chromosomal breaks which suggested that there were sites of fragility. Meiotic diakinesis showed multiple chromosomal rings, indicating the occurrence of multiple translocations, as previously reported by other investigators. These data suggest that, in addition to fission and fusion, other chromosomal rearrangements were probably involved in the differentiation of the karyotypes of these species of Eleutherodactylus, especially E. binotatus.

Resumo em Inglês:

Previously, only partial P element sequences have been reported in the saltans group of Drosophila but in this paper we report two complete P element sequences from Drosophila sturtevanti and Drosophila prosaltans. The divergence of these sequences from the canonical P element of Drosophila melanogaster is about 31% at the nucleotide level. Phylogenetic analysis revealed that both elements belong to a clade of divergent sequences from the saltans and willistoni groups previously described by other authors.

Resumo em Inglês:

The velvetbean caterpillar (VBC), Anticarsia gemmatalis Hübner, 1818 (Insecta: Lepidoptera: Noctuidae), is one of the most important New World soybean agro-ecosystems pests, occurring from 40° N in the USA to 39° S in Argentina. Information on the migration patterns of the VBC moth may be important for managing the resistance of VBC populations to insecticides or plants carrying the Bacillus thuringiensis insecticide genes, especially since sedentary populations have a higher potential to became resistant than migratory populations. We studied intraspecific variations of geographically distinct VBC populations in order to determine the genetic distance between them and to assess the variability of VBC populations from near the city of Londrina (Paraná (PR) state, Brazil). Samples of the VBC were obtained from sites near the following towns or cities: Marianna and Quincy (Florida, USA); La Virginia (Tucumán province, Argentina); Londrina (PR), Passo Fundo (Rio Grande do Sul, Brazil) and Planaltina (Goiás, Brazil). The VBC samples were used to construct a genetic similarity matrix based on random amplified polymorphic DNA (RAPD) allele frequencies, the cotton leafworm, Alabama argillacea, Hübner 1823 (Insecta: Lepidoptera: Noctuidae), being used as an outgroup. Interestingly, despite the great distance (about 6,500 km) between Planaltina and Quincy some of the specimens from the Quincy population clustered in a group genetically close to the Planaltina populations. Larvae collected on peanuts in Marianna and on soybean in Quincy, 70 km apart, appeared genetically similar. The population from Planaltina was the most heterogeneous (polymorphism = 85.6%; heterozygosity = 0.1505). The Argentinean VBC population was entirely different from the Brazilian populations. The genetic similarities found between individuals from geographically distant populations and effective migration rate values (2.0566 > Nm < 15.2618) indicate that migration occurs.

Resumo em Inglês:

Gene variation and population genetic structure of the Neotropical sawfly Digelasinus diversipes were measured by allozyme analyses using starch gel electrophoresis. Cocoon masses were collected in Eugenia glazioviana (Myrtaceae) stems, in two areas of the "Estação Ecológica Jataí" (Luiz Antônio, SP, Brazil - 21°25' S, 47°50' W), in 2000 and 2001. The average heterozygosity observed in this species (Hobs = 0.094 ± 0.025) was not significantly different from other Symphyta groups; it was, however, significantly higher than in other Hymenoptera populations. No significant levels of inbreeding were found (F IS = 0.062; chi2 = 29.9; p > 0.05), but the population was subdivided (F ST = 0.070; chi2 = 458.9; p < 0.05), suggesting the absence of a significant gene flow among the samples studied, due to limited dispersion ability. The low relatedness coefficients found (ranging from 0.23 ± 0.09 to 0.44 ± 0.10) suggest that larvae from different ovipositions associate to construct the cocoon masses.

Resumo em Inglês:

Anteaters belong to the Order Xenarthra / Family Myrmecophagidae and are the only members without teeth. There are three genera with four living species in the family Myrmecophagidae: Myrmecophaga tridactyla (giant anteater), Tamandua tetradactyla (southern lesser anteater), Tamandua mexicana (northern lesser anteater), and Cyclopes didactylus (silky anteater). The karyotypes of M. tridactyla (2n = 60), T. tetradactyla (2n = 54) and C. didactylus (2n = 64) have already been described. In the present paper, three female and two male specimens of giant anteater and one lesser anteater male were analyzed. The results indicate the existence of a new karyotype in the genus Tamandua, with 2n = 56 chromosomes, which can represent a new lesser anteater species. The karyotype of M. tridactyla was also described, supporting previous reports.

Resumo em Inglês:

Seven soybean cultivars (Bossier, Cristalina, Davis, Kent, Lincoln, Paraná and Uberaba), with different levels of resistance to Cercospora sojina, race 04, were crossed according to a diallel design, with no reciprocals, to determine the general and the specific combining abilities for the resistance. The evaluations of the reaction to the disease were performed 20 days after the inoculation of the fungus on the most infected leaflet of the plant, in the parents and in the F1 hybrids. To quantify the resistance, the following characteristics were evaluated: infection degree (ID); number of lesions per leaflet (NLL); lesion mean diameter (LMD); lesioned leaf area (LLA); percentage of lesioned leaf area (PLLA); number of lesions per square centimeter (NLC) and disease index (DI). The relative importance of each characteristic was evaluated by the canonical variables analysis and the LLA and NLL characteristics were eliminated from the multivariate function. With the remaining five characteristics, a multivariate index was created using the first canonical vector, which was submitted to the diallel analysis, according to Griffings fixed model, method 2. The most important characters to discriminate resistant from susceptible soybean plants to C. sojina were: ID, LMD, NLC, DI and PLLA. Cristalina, Davis and Uberaba cultivars are the best ones among those tested that can be recommended as parents in soybean breeding programs seeking resistance to Cercospora sojina. The additive, dominant and epistatic genetic effects were important for the expression of the resistance, although the additive genetic effect was the most important component.

Resumo em Inglês:

In order to study the genetic control of soybean resistance to sudden death syndrome (SDS), a 5 x 5 diallel with the F2 generation, without the reciprocals, was carried out in a greenhouse. The following parents were used: Forrest, MG/BR-46 (Conquista), IAC-4, FT-Cristalina, and FT-Estrela. The first two cultivars are more resistant to SDS than IAC-4, which is considered to be moderately resistant to SDS, and the last two cultivars are highly susceptible. The fungus was inoculated with three colonized sorghum grains placed at the bottom of the holes with two soybean seeds. Single plants were evaluated between 14 and 37 days after emergency based on foliar severity symptoms (1-5) of SDS. The disease incidence and a disease index were also calculated for each plot (clay pots with five plants each). The analysis for severity and disease index was performed only with the data of the 37th day after emergence. Additive and dominant genetic effects were detected by Jinks-Hayman's analysis, but the dominant genetic effects were higher. The genetic parameters estimated indicated that the average degree of dominance showed the presence of overdominance; at least three loci or genic blocks that exhibited dominance were responsible for the genetic control of SDS resistance; the estimates of narrow-sense heritabilities were moderate (0.48 to 0.62), but in the broad-sense they were higher (0.90 to 0.95), thus reinforcing the presence of dominance effects; and the resistance to SDS was controlled mostly by dominant alleles. Five microsatellite markers (Satt163, Satt309, Satt354, Satt371 and Satt570), reported as linked to five QRLs of the SDS, were used to genotype the parents and showed the possibility of occurrence of multiallelism in those loci, but this evidence did not invalidate the fitting of the data to the Jinks-Hayman's model.

Resumo em Inglês:

A matrix approach is described for assessing the variance of effects in incomplete diallels designs. The method is illustrated by reference to simulated complete and incomplete diallels using different combinations of constraints, average degree of dominance and, for the incomplete diallel, number of hybrids. Our results showed that caution should be taken in working with incomplete diallels under conditions of overdominance because there were changes in the rank of the genotypes when the excluded hybrid had parents with a low frequency of the favorable allele (i.e. the allele which increases expression of a character). The expression described in this paper is a rapid and safe approach to estimate variances and covariances of the effects of contrasts of incomplete diallels.

Resumo em Inglês:

Senna multijuga is a pioneer tropical tree species that occurs mainly in the Brazilian Atlantic forest. We investigated the mating system of two populations of S. multijuga, one located in a reserve area (RD1) and the other (RD2) about 15 km away. The mating system parameters were estimated using the mixed mating model (software MLTR). The two populations had significantly different outcrossing rates, with population RD2 having a high rate (t m = 0.838) and population RD1, a lower rate (t m = 0.540). The values of t s were different between the two populations and also lower than those of t m. Significant t m - t s estimates indicated that biparental inbreeding contributed to the apparent selfing rate in these populations. The correlation of paternity was significant in population RD2 (r p = 0.309), suggesting that the progeny were more closely related than inferred by the observed outcrossing rate. The estimates of correlation of paternity, biparental inbreeding and the significant differences in pollen and ovule allele frequencies indicated that population RD2 is genetically substructured. For a pioneer species such as S. multijuga, selfing can be an important strategy for occupying open areas.

Resumo em Inglês:

The mating system and genetic diversity were studied in a natural population of Myracrodruon urundeuva originating from 30 open-pollinated trees at the Paulo de Faria Ecological Station, SP, Brazil. The progenies were planted on the Teaching and Research Farm of the Ilha Solteira Engineering School, UNESP. Using the fAFLP molecular marker, eleven loci were selected to study the mating system. The mating system was analyzed using the multilocus mixed-mating model. The estimates of genetic divergence between pollen and ovule allele frequencies were significant for eight loci, suggesting nonrandom outcrossing. The estimates of the multilocus outcrossing rate revealed that M. urundeuva possesses a mating system with a predominance of outcrossing events (theta = 0.940 ± 0.086). The estimates of coancestry among plants within progenies (theta = 0.185) was higher than that expected for half-sib progenies (0.125) and the indirect estimate of the correlation of outcrossed paternity within progeny arrays (r p) was 0.403, suggesting that progenies have a high proportion of full-sibs. Result analysis suggests the need for the application of biometric models that take into account deviations from random outcrossing in the estimations of genetic parameters for quantitative traits and the need for retaining large sample sizes in order to preserve genetic variability.

Resumo em Inglês:

A genetic analysis of adult plant resistance to leaf rust (Puccinia triticina) was performed in in vitro obtained double haploid progenies from a cross between the Brazilian wheat cultivar Trigo BR 35, which, under the high inoculum pressure of the southern region, has been resistant to leaf rust for more than 12 years, and the susceptible cultivar IAC 13-Lorena. Haplodiploidization via in vitro gimnogenesis was done by somatic elimination of the pollen donor genome after maize pollination of the F1 plants. The advantages and usefulness of double haploids (DH) for genetic analysis of complex inherited traits like durable adult-plant resistance to wheat leaf rust were evident: it was possible to analyze inheritance patterns in this cross by using only the 35 DH homozygous segregant lines obtained by in vitro embryo culture of F1 flowers pollinated by maize, this number being equivalent to 1,225 conventional F2 lines because of lack of heterozygosity. After being infected with MCG and LPG races, the results indicated that Trigo BR 35 has two resistance genes. One of the genes expressed resistance only after the intermediate stage of plant development (5-6 leaves).

Resumo em Inglês:

The objective of this work was to analyze the effects of RAPD markers with skewed segregation on genetic linkage maps. Segregation data for 123 Citrus sinensis (L.) Osbeck cv. Pêra markers and 53 C. reticulata Blanco cv. Cravo markers in F1 progeny composed of 94 hybrids were used. Genetic linkage maps of the two varieties were constructed with non-skewed markers (p < 0.05 and p < 0.01) using the program MAPMAKER 3.0 and a pseudo-testcross strategy. The maps were compared to those constructed with all markers. Alterations in the genetic distances were observed based on the location of the skewed markers within the linkage groups. Generally, the skewed markers were located at the end of the linkage groups, sometimes forming entire linkage groups, without causing significant distance modifications. However, skewed markers located between non-skewed markers caused significant distance modifications and, in some cases, altered the order of the markers. Most of the skewed markers can be included in linkage maps, but in each case the degree of distance modification caused by each marker needs to be assessed.

Resumo em Inglês:

Attempts to obtain a recombinant protein using prokaryotic expression systems can go from a rewarding and rather fast procedure to a frustrating time-consuming experience. In most cases production of heterologous proteins in Escherichia coli K12 strains has remained an empirical exercise in which different systems are tested without a careful insight into the various factors affecting adequate expression of the encoded protein. The present review will deal with E. coli as protein factory and will cover some of the aspects related to transcriptional and translational expression signals, factors affecting protein stability and solubility and targeting of proteins to different cell compartments. Based on the knowledge accumulated over the last decade, we believe that the rate of success for those dedicated to expression of recombinant proteins based on the use E. coli strains can still be significantly improved.

Resumo em Inglês:

The effect of four antibiotics (amikacin, clindamycin, cephalothin and vancomycin) was investigated considering that bacterial infection in fibroblasts cultures is a very frequent event. The investigation included the effect of the antibiotics on fibroblast growth and on the activity of the enzyme glucocerebrosidase. The antibiotics were added to the fibroblast cultures and cell growth was evaluated by counting the number of cells and their viability. After cell harvesting, the enzyme activity and content of protein were measured. The results allowed us to conclude that none of the antibiotics affected the cellular number nor the cellular viability. The content of protein decreased when cephalothin and clindamycin were added to the cultures, and glucocerebrosidase was affected in the presence of amikacin. Vancomycin did not interfere with any of the parameters analyzed, so it was chosen to be used in cell cultures to prevent the contamination by gram positive bacteria.

Resumo em Inglês:

The biological effects of microwaves on living organisms remain highly controversial. Although some reports have suggested that microwaves may be directly or indirectly genotoxic, a direct action is unlikely because the low energy of microwave photons makes them unable to cause single-strand breaks in DNA. In this work, we examined the possible clastogenic properties of microwaves (2.5 and 10.5 GHz) on blood lymphocytes in vitro by monitoring the frequency of chromosomal aberrations. We also investigated whether blood cells showed increased radiosensitivity or radioresistance when pretreated with the microwaves and then irradiated with gamma radiation. There was no significant difference in the frequency of chromosomal aberrations between cells which had or had not been treated with microwaves. Control cells had a mean frequency of 0.013 aberrations per cell compared to 0.010 and 0.011 aberrations per cell in the microwave-exposed samples. Nor was there any alteration in the radiosensitivity of cells pretreated with microwaves. Gamma irradiated cells showed a mean frequency of 0.279 aberrations per cell compared to 0.343 and 0.310 aberrations per cell in samples pretreated with microwaves. However, cell mortality increased markedly after exposure to microwaves. The results suggest that microwaves do not interact directly or indirectly with chromosomes, although they may target other cell structures, such as cell membranes.

Resumo em Inglês:

The so-called Evolutionary Synthesis, the present paradigm for evolutionary explanations, was established during the 1920s, 1930s and 1940s. One of the leading scientists contributing to this was Theodosius Dobzhansky, a Russian born geneticist who emigrated to the United States of America in 1927 to study with Thomas Hunt Morgan. He was also responsible for the development of Drosophila genetics in Brazil, which was the main organism employed in experimental studies of evolution. Dobzhansky had several opportunities to visit Brazil starting in 1943, to do field and laboratory work as well as teaching. All these activities were fundamental in the spreading of new concepts, methodology, and objectives of the Synthesis to a new audience. This paper discusses the results of the interaction between Dobzhansky and a group of young Brazilian researchers, particularly from the University of São Paulo.