Scielo RSS <![CDATA[Genetics and Molecular Biology]]> http://www.scielo.br/rss.php?pid=1415-475720050003&lang=en vol. 28 num. 3 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.br/img/en/fbpelogp.gif http://www.scielo.br <![CDATA[<B>Antonio Carlos Garros Stort (1939-2005)</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300001&lng=en&nrm=iso&tlng=en <![CDATA[<B>Cora de Moura Pedreira (1915-2005)</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300002&lng=en&nrm=iso&tlng=en <![CDATA[<B>Effects of cytoplasmic inheritance on preweaning traits of Hereford cattle</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300003&lng=en&nrm=iso&tlng=en The influence of cytoplasmic inheritance on birth and weaning weight was evaluated in an experimental Hereford herd. Data on 1,720 records for birth and weaning weights from calves born between 1963 and 2002 were studied. Variance components were estimated using MTDFREML procedures and an animal model was fitted for each trait. Direct and maternal additive effects and permanent environment and maternal lineage effects were treated as random, while year and month of birth, age of dam and sex of the calf were treated as fixed. Identification of maternal lineages was based on pedigree information. The contribution to phenotypic variance of cytoplasmic lineages defined by pedigree information was negligible for both traits. Mitochondrial genotypes of cows present in the herd in 2002 were analyzed by single strand conformation polymorphism (SSCP) analysis. Only five different genotypes were identified among 23 maternal lineages. All the animals with records were assigned to maternal genotypes based on pedigree information. The statistical analysis was repeated, removing maternal lineage from the model and including mitochondrial genotype as a fixed effect. No evidence of genotype effects was detected. These results suggest a negligible effect of the mitochondrial genome on the preweaning traits of this Hereford herd. <![CDATA[<B>Association of MYF5 gene allelic variants with production traits in pigs</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300004&lng=en&nrm=iso&tlng=en We studied the phenotypic effects of polymorphisms at the MYF5 gene in a divergent F2 swine population and found that one polymorphism was due to an insertion and another to a deletion. The genotypes of 359 F2 animals were obtained and the Normal/Normal (NN) and Normal/Insertion (NI) genotypes analyzed to determine associations with phenotypic data for performance, carcass and meat quality traits. Significant differences were observed (p < 0.05) between NN and NI animals for drip (NN = 3.14 &plusmn; 1.56; NI = 3.69 &plusmn; 2.78%), cooking (NN = 32.26 &plusmn; 2.41; NI = 33.21 &plusmn; 2.31%) and total loss (NN = 34.16 &plusmn; 2.63 and NI = 34.97 &plusmn; 2.08%). The Deletion marker was not statistically tested. The results indicate that the allelic variant Insertion is associated with a deleterious effect on meat quality traits and should be monitored in marker assisted selection programs. <![CDATA[<B>Genetic variability of <I>Hypostomus</I> (Teleostei, Loricariidae) from the Ribeirão Maringá, a stream of the upper Rio Paraná basin, Brazil</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300005&lng=en&nrm=iso&tlng=en Hypostomus strigaticeps and two morphotypes of Hypostomus were collected from Ribeirão Maringá, a small tributary of the Rio Pirapó, an effluent of the upper Rio Paraná. The three populations were analyzed by allozyme electrophoresis that allowed the scoring of 25 loci from 14 enzyme systems. Heterozygosity values (He) were 0.028 in H. strigaticeps, 0.027 in Hypostomus sp. 1 and zero in Hypostomus sp. 2. Several diagnostic loci and fixed differences were observed for each population at loci Acp-A, Gcdh-A and Mdhp-A. Thus, all populations were genetically distinct, although there were many common alleles. The unbiased genetic identities of Nei (I) were estimated as 0.780 for Hypostomus sp. 1 and H. strigaticeps, 0.357 for H. strigaticeps and Hypostomus sp. 2 and 0.322 for Hypostomus sp. 1 and Hypostomus sp. 2. The data indicate that the two morphotypes are distinct species from Hypostomus strigaticeps. <![CDATA[<B>Karyotype, C-and fluorescence banding pattern, NOR location and FISH study of five Scarabaeidae (Coleoptera) species</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300006&lng=en&nrm=iso&tlng=en Meiotic chromosomes obtained from members of the coleopteran subfamilies Rutelinae and Dynastinae were studied using standard and silver nitrate staining, C-banding, base-specific fluorochromes and fluorescent in situ hybridization (FISH). The study presents detailed karyotipic descripitions of three Rutelinae species (Geniates borelli, Macraspis festiva and Pelidnota pallidipennis), and two Dynastinae species (Lygirus ebenus and Strategus surinamensis hirtus) with special emphasis on the distribution and variability of constitutive heterochromatin and the nucleolar organizer region (NOR). We found that for G. borelli, P. pallidipennis, L. ebenus and S. s hirtus the karyotype was 2n = 20 (9II + Xy p), with G. borelli, P. pallidipennis and L. ebenus showed meta-submetacentric chromosomes which gradually decreased in size. For Macraspis festiva the karyotype was 2n = 18 (8II + Xy p). In L. ebenus we found that the NOR was located on an autosome, but in the other four species it occurred on the sex bivalents. In all five species the constitutive heterochromatin (CH) was predominantly pericentromeric while the X chromosomes were almost completely heterochomatic, although CMA3/DA/DAPI staining showed intra and interspecific variation in the bright fluorescence of the constitutive heterochromatin. The FISH technique showed rDNA sites on the X chromosome of the Rutelinae species. <![CDATA[<B>Equine protease inhibitor system as a marker for the diagnosis of chronic obstructive pulmonary disease (COPD)</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300007&lng=en&nrm=iso&tlng=en The protease inhibitor system (PI) was investigated to ascertain if it can be used as a marker of chronic obstructive pulmonary disease (COPD) in thoroughbred horses. Serum samples were taken from healthy thoroughbreds (n = 13) and those diagnosed as having COPD (n = 24) or inflammatory airway disease (IAD, n = 38) as well as from 3,600 undiagnosed thoroughbred horses. PI allelic and genotypic frequencies were estimated using protein electrophoresis on starch and polyacrylamide gels. The four groups of horses showed high genotypic similarity and none of the observed alleles or genotypes of the equine PI system were found to be associated with COPD. <![CDATA[<B>LEI0258 microsatellite variability and its relationship to <I>B-F</I> haplotypes in Brazilian (blue-egg Caipira) chickens</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300008&lng=en&nrm=iso&tlng=en A total of 149 chickens from two different sources (one non-commercial, the other commercial) was tested for variability of the LEI0258 microsatellite. Fifty- three genotypes, explainable by 15 alleles, were found. There are clear allele and heterozygosity differences between the two samples. One of them was simultaneously studied for the MHC B-F haplotypes. Strong genetic disequilibrium was observed between the variants of the two systems, therefore providing a cheap alternative for MHC genotyping. <![CDATA[<B>Karyotype characterization of <I>Trigona fulviventris</I> Guérin, 1835 (Hymenoptera, Meliponini) by C banding and fluorochrome staining</B>: <B>report of a new chromosome number in the genus</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300009&lng=en&nrm=iso&tlng=en Although many species of the genus Trigona have been taxonomically described, cytogenetic studies of these species are still rare. The aim of the present study was to obtain cytogenetic data by conventional staining, C banding and fluorochrome staining for the karyotype characterization of the species Trigona fulviventris. Cytogenetic analysis revealed that this species possesses a diploid chromosome number of 2n = 32, different from most other species of this genus studied so far. This variation was probably due to the centric fusion in a higher numbered ancestral karyotype, this fusion producing the large metacentric chromosome pair and the lower chromosome number observed in Trigona fulviventris. Heterochromatin was detected in the pericentromeric region of the first chromosome pair and in one of the arms of the remaining pairs. Base-specific fluorochrome staining with 4'-6-diamidino-2-phenylindole (DAPI) showed that the heterochromatin was rich in AT base pairs (DAPI+) except for pair 13, which was chromomycin A3 (CMA3) positive indicating an excess of GC base pairs. Our data also suggests that there was variation in heterochromatin base composition. <![CDATA[<B>Camperdown hemoglobin associated with <FONT FACE=Symbol>b</FONT>° thalassemia in a Brazilian child</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300010&lng=en&nrm=iso&tlng=en We report the coexistence of Hb Camperdown [beta104 (G6) Arg -> Ser] and beta&deg;-thalassemia [beta39 (Gln -> stop codon)] in a nine-month-old Brazilian boy. He had a relatively more severe hypochromic and microcytic anemia in comparison to his mother's beta-thalassemia trait. His Hb Camperdown heterozygous father was clinically and hematologically normal. To our knowledge, this is the first description of an association of beta&deg;-thalassemia with Hb Camperdown. <![CDATA[<B>Polymorphisms of the DNA repair genes <I>XRCC1</I> and <I>XRCC3</I> in a Brazilian population</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300011&lng=en&nrm=iso&tlng=en In several DNA repair genes, polymorphisms may result in reduced repair capacity, which has been implicated as a risk factor for various types of cancer. The frequency of the polymorphic alleles varies among populations, suggesting an ethnic distribution of genotypes. We genotyped 300 healthy Southeastern Brazilian individuals (262 of European ancestry and 38 of African ancestry) for polymorphisms of codons 194 and 399 of the XRCC1 base excision repair pathway gene and of codon 241 of the XRCC3 homologous recombination repair pathway gene. The allele frequencies were 0.07 for the Arg194Trp and 0.33 for the Arg399Gln codons of the XRCC1 gene and 0.35 for the Thr241Met codon of the XRCC3 gene. The genotypic frequencies were within Hardy-Weinberg equilibrium. These frequencies showed ethnic variability when compared with those obtained for different populations from several countries. <![CDATA[<B>Valongo, genetic studies on an isolated Afro-Brazilian community</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300012&lng=en&nrm=iso&tlng=en A southern Brazilian isolated community of predominantly sub-Saharan African origin, with a total population of 74 individuals and high degree of inbreeding (F = 0.081) was studied. The small sizes of the breeding (35) and effective (21) populations, as well as the very small effective migration rate (4%), suggest a high probability for the occurrence of genetic drift. A sample was typed for fourteen blood genetic systems and most of these systems seem to reveal the founder effect. This evolutionary factor was probably responsible for the absence of some polymorphic alleles frequent in African populations, i.e.: ABO*B, RHD-RHCE*DCe, GPA-GPB*NS (MNSs*NS), GPA-GPB*NS U (MNSs*NSU), HBB*S, HP*2M and ESD*2. The most unusual allele frequency was that for BCHE*A, 0.27, four times higher than its highest estimated frequency and fifty times higher than that those observed in African populations. Considering the allele frequencies of the Sub-Saharan African (A) and European (E) ancestral populations, the population studied can be quantified as containing 97.33% &plusmn; 10.41 of A alleles and 2.67% &plusmn; 10.41 of E alleles. <![CDATA[<B>Genetic structure of natural <I>Eugenia dysenterica DC</I> (Myrtaceae) populations in northeastern Goiás, Brazil, accessed by morphological traits and RAPD markers</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300013&lng=en&nrm=iso&tlng=en The Brazilian Cerrado (Savannah) is a biome with great biodiversity. Many of the species found in this biome have unlimited economic potential and are used by the local population for various purposes. With the opening of the agricultural frontiers in this region, much of the native flora has been replaced by extensive areas of monocultures. Thirteen populations of the Eugenia dysenterica DC species were sampled in the northeast of the state of Goiás, Brazil, to analyze their genetic structure. Morphological traits were measured for all the progeny obtained and some of them were analyzed by using RAPD markers. The natural populations of the species showed high levels of variability for the morphological traits. The phenotypic, genotypic and genetic variabilities as structured in these populations were highly significant among populations, although most of the variability was detected within populations. The phenotypic and genetic variabilities were structured spatially as shown by the positive and highly significant correlation coefficients between the phenotypic and genetic distance matrixes and the geographic distance matrix. The ideal conservation strategy for the species in the region requires sampling of a high number of individuals of each population and also a significant number of populations to ensure suitable effective population sizes. <![CDATA[<B>Genetic variability and selection for laticiferous system characters in <I>Hevea brasiliensis</B></I>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300014&lng=en&nrm=iso&tlng=en Six laticiferous system characters were investigated in 22 three-year-old, half-sib rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell.-Arg.] progenies, evaluated at three sites (Votuporanga, Pindorama and Jaú, all in the São Paulo State, Brazil). The traits examined were: average rubber yield (Pp), average bark thickness (Bt), number of latex vessel rings (Lv), average distance between consecutive latex vessel rings (Dc), density of latex vessels per 5 mm per ring averaged over all rings (Dd) and the diameter of the latex vessels (Di). The joint analysis showed that site effect and progeny x sites interaction were significant for all traits, except Lv. Estimates of individual heritabilities across the three sites were high for Bt; moderate for Lv, Pp and Dc; low for Dd and very low for Di. Genetic correlations in the joint analysis showed high positive correlations between Pp and the other traits. Selecting the best five progenies would result in genetic gains of 24.91% for Pp while selecting best two plants within a progeny would result in a Pp genetic gain of 30.98%. <![CDATA[<B>Somaclonal variation in <I>Asparagus officinalis</I> plants regenerated by organogenesis from long-term callus cultures</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300015&lng=en&nrm=iso&tlng=en Somaclonal variation in plants regenerated by organogenesis from long-term cultured calluses of two diploid staminate genotypes of Asparagus officinalis cv. Argenteuil was characterized by plant phenotype, ploidy, meiotic behavior, pollen viability, fruit and seed set, and AFLP profiles. Phenotypic deviations from the donors were detected in foliage color, flower size, and cladode and flower morphology. Ploidy changes were observed in 37.8% of the 37 regenerants studied. Meiotic alterations in 12 out of 21 regenerants included laggards, dicentric bridges, micronuclei, restitution nuclei and polyads. Of the 408 AFLP markers screened in 43 regenerants and the donors, 2.94% showed polymorphism. High pollen viability was observed in the 22 regenerants analyzed. All crosses between one pistillate plant and 35 regenerants, as well as the controls, produced fruits and seeds; however, no plump seeds resulted in 35.3% of the crosses with regenerants, and no seeds germinated in 12.5% of those with apparently normal seeds. Fruit and seed set was similar in crosses with diploid regenerants with normal meiosis and the controls but was lower in crosses with diploid and polyploid regenerants with abnormal meiosis. Our results show that the regenerated plants exhibited conspicuous somaclonal variation that could be eventually exploited for in vitro selection systems. <![CDATA[<B>An approach for understanding the heredity of two quality traits (head color and tightness) in globe artichoke (<I>Cynara scolymus</I> L.)</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300016&lng=en&nrm=iso&tlng=en The inheritance of head color and tightness in globe artichoke was studied utilizing crosses between inbreed lines and between clones and self-pollinated clones from different genetic origins. These genetic materials were sowed in a completely randomized design with 20 plants per plot and genotype. Globe artichoke heads were classified into three colors (purple-green, purple and green) and three head tightness types (compact, fairly compact and soft) and the segregating ratios for these traits tested in each offspring using the chi-square test. Crosses between green and purple inbreed lines produced only purple-green heads but F2 generation segregated at a purple-green:purple:green ratio of 9:3:4. The self-pollinated compact head clones produced a compact head:fairly compact head:soft head ratio of 12:3:1. The remaining crosses between lines and among clones and backcrosses verified these ratios. These results suggest that two loci with a simple recessive epistasis are involved in the inheritance of head color and that two loci with simple dominant epistasis are involved in the expression of the different head tightness types. The inheritance models proposed here could be helpful in predicting the appearance of artichoke heads if breeders need to obtain hybrid seeds for a desirable phenotype. <![CDATA[<B>New resistance genes in the <I>Zea mays</B></I>: <B><I>exserohilum turcicum</I> pathosystem</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300017&lng=en&nrm=iso&tlng=en The use of monogenic race-specific resistance is widespread for the control of maize (Zea mays L.) helminthosporiosis caused by Exserohilum turcicum. Inoculation of 18 Brazilian isolates of E. turcicum onto elite maize lines containing previously identified resistance genes and onto differential near-isogenic lines allowed the identification of new qualitative resistance genes. The inoculation of one selected isolate on differential near-isogenic lines, F1 generations and a BC1F1 population from the referred elite lines enabled the characterization of the resistance spectrum of three new genes, one dominant (HtP), one recessive (rt) and a third with non-identified genetic action. Three physiological races of the pathogen were also identified including two with new virulence factors capable of overcoming the resistance of one of the resistance genes identified here (rt). <![CDATA[<B>Absence of the A4 peptide in the G4 glycinin subunit of soybean cultivar Enrei is caused by a point mutation in the <I>Gy4</I> gene</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300018&lng=en&nrm=iso&tlng=en Functional properties of soy proteins for food are closely related to the composition of their storage protein subunits. Using base excision sequence scanning (BESS), we show that the absence of the A4 peptide in the G4 glycinin subunit of the soybean (Glycine max L.) cultivar Enrei was caused by the same point mutation in the Gy4 gene as previously reported in the soybean cultivar Raiden. Although the genetic relationship between Raiden and Enrei is not known, the same point mutation in their Gy4 genes may indicate that they probably share a related origin. The application of BESS to identify single nucleotide polymorphisms (SNPs) as co-dominant markers for marker-assisted selection (MAS) of a recessive null allele is also discussed. <![CDATA[<B>What is new on plant cytogenetics?</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300019&lng=en&nrm=iso&tlng=en Functional properties of soy proteins for food are closely related to the composition of their storage protein subunits. Using base excision sequence scanning (BESS), we show that the absence of the A4 peptide in the G4 glycinin subunit of the soybean (Glycine max L.) cultivar Enrei was caused by the same point mutation in the Gy4 gene as previously reported in the soybean cultivar Raiden. Although the genetic relationship between Raiden and Enrei is not known, the same point mutation in their Gy4 genes may indicate that they probably share a related origin. The application of BESS to identify single nucleotide polymorphisms (SNPs) as co-dominant markers for marker-assisted selection (MAS) of a recessive null allele is also discussed. <![CDATA[<B>Genetic diversity of <I>Xanthomonas axonopodis</I> pv. citri based on plasmid profile and pulsed field gel electrophoresis</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300020&lng=en&nrm=iso&tlng=en Xanthomonas axonopodis pv. citri strains that cause disease in citrus were investigated by pulsed field and plasmid profile analysis. For the first method, genomic DNA was digested by the rare-cutting enzymes Xba I and Vsp I. The strains evaluated were collected in seven different States of Brazil and in Argentina, Bolivia, Paraguay and Uruguay. Genetic variability was found among strains of X. axonopodis pv. citri from different geographical areas Argentina, Bolivia and Uruguay, with similarities varying from 0.62 to 0.83. However, the strains collected in Brazil, despite being from different States, have shown a genetic similarity ranging from 0.83 to 1.00. Cluster analysis showed a relationship between genomic similarity and geographical origin of the strains. Plasmids were observed in all strains, with a total of five different plasmids, with sizes between 57.7 and 83.0 kilobases. The 72.6 kb plasmid was the most frequent, present in 15 out of 22 strains, while the 68.1 kb plasmid was observed in two strains only. Although the plasmid diversity detected in the present study was not very great, the X. axonopodis pv. citri strains evaluated showed a considerable degree of diversity with regard to this extrachromosomal genetic element. <![CDATA[<B>Dose assessment by quantification of chromosome aberrations and micronuclei in peripheral blood lymphocytes from patients exposed to gamma radiation </B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300021&lng=en&nrm=iso&tlng=en Scoring of unstable chromosome aberrations (dicentrics, rings and fragments) and micronuclei in circulating lymphocytes are the most extensively studied biological means for estimating individual exposure to ionizing radiation (IR), which can be used as complementary methods to physical dosimetry or when the latter cannot be performed. In this work, the quantification of the frequencies of chromosome aberrations and micronuclei were carried out based on cytogenetic analyses of peripheral blood samples from 5 patients with cervical uterine cancer following radiotherapy in order to evaluate the absorbed dose as a result of partial-body exposure to 60Co source. Blood samples were collected from each patient in three phases of the treatment: before irradiation, 24 h after receiving 0.08 Gy and 1.8 Gy, respectively. The results presented in this report emphasize biological dosimetry, employing the quantification of chromosome aberrations and micronuclei in lymphocytes from peripheral blood, as an important methodology of dose assessment for either whole or partial-body exposure to IR. <![CDATA[<B>Genotoxic and antigenotoxic effects of organic extracts of mushroom <I>Agaricus blazei</I> Murrill on V79 cells </B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300022&lng=en&nrm=iso&tlng=en Agaricus blazei Murrill, popularly known as the sun mushroom, is a native mushroom in SP, Brazil, that has been widely used in the treatment of cancer and many other pathologies in different parts of the world. A water-soluble protein-polysaccharide complex (1 -> 6)beta-D-glucan has been isolated from its fruiting body that showed immune-modulation activity. From organic extracts, linoleic acid has been isolated and determined to be the main substance with antimutagenic activity. Using both the micronucleus (MN) and comet (single cell microgel electrophoresis) assays, this study determined the genotoxic and antigenotoxic potential of A. blazei (AB) obtained from commercial sources or the following strains: a) strains AB 97/29 (young and sporulated phases); b) a mixture taken from AB 96/07, AB 96/09 and AB 97/11 strains; and c) commercial mushrooms from Londrina, PR and Piedade, SP, designated as AB PR and AB SP, respectively. The extracts from these mushrooms were isolated in chloroform:methanol (3:1) and used in vitro at three different concentrations. V79 cells (Chinese hamster lung cells) were exposed to the extracts under pre-, simultaneous and post-treatment conditions, combined with methyl methanesulfonate (MMS). Under the circumstances of this study, these organic extracts did not show any genotoxic or mutagenic effects, but did protect cells against the induction of micronuclei by MMS. <![CDATA[<B>Comet assay comparison of different <I>Corbicula fluminea</I> (Mollusca) tissues for the detection of genotoxicity </B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300023&lng=en&nrm=iso&tlng=en The comet assay was used to study the sensitivity of the widely distributed freshwater bivalve mollusk Corbicula fluminea to the DNA-damaging alkylating-agent methylmethane sulfonate (MMS). This study was undertaken to ascertain if C. fluminea is a good bioindicator of pollutants in aquatic environments and identify which C. fluminea tissue is most effective and practical for genotoxicity studies. The mollusks were exposed to 0.6, 1.2 or 2.4 X 10-4 M MMS for 40 min and their hemolymph, gill tissue and digestive gland tissue assessed for the level of DNA damage and the time needed for the tissues to recovery. Regression analysis showed a direct linear dose-response relationship between MMS concentration and the number of damaged cells for hemolymph and digestive gland tissue but a quadratic relationship for gill tissue, which made the interpretation the gill tissue results difficult. The basal level of DNA damage to gill tissue was very high, possibly because gill is the organs most directly exposed to environmental toxins and mutagenic agents. Although all three types of tissue produced useful results, hemolymph and digestive gland tissue produced more reproducible and reliable results. Hemolymph was the best sample type in that it was easy to obtain and handle, while gill tissue required more manipulation to obtain cell suspensions. Our results indicate that C. fluminea is an optimal bioindicator for the determination genotoxic contaminants in aquatic environments. <![CDATA[<B>Increased micronucleated cell frequency related to exposure to radiation emitted by computer cathode ray tube video display monitors </B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300024&lng=en&nrm=iso&tlng=en It is well recognized that electromagnetic fields can affect the biological functions of living organisms at both cellular and molecular level. The potential damaging effects of electromagnetic fields and very low frequency and extremely low frequency radiation emitted by computer cathode ray tube video display monitors (VDMs) has become a concern within the scientific community. We studied the effects of occupational exposure to VDMs in 10 males and 10 females occupationally exposed to VDMs and 20 unexposed control subjects matched for age and sex. Genetic damage was assessed by examining the frequency of micronuclei in exfoliated buccal cells and the frequency of other nuclear abnormalities such as binucleated and broken egg cells. Although there were no differences regarding binucleated cells between exposed and control individuals our analysis revealed a significantly higher frequency of micronuclei (p < 0.001) and broken egg cells (p < 0.05) in individuals exposed to VDMs as compared to unexposed. We also found that the differences between individuals exposed to VDMs were significantly related to the sex of the individuals and that there was an increase in skin, central nervous system and ocular disease in the exposed individuals. These preliminary results indicate that microcomputer workers exposed to VDMs are at risk of significant cytogenetic damage and should periodically undergo biological monitoring. <![CDATA[<B>The phenotype strikes back and is out on more than one limb</B>: <B>a review of <I>Developmental Plasticity and Evolution</I>, by Mary Jane West-Eberhard</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300025&lng=en&nrm=iso&tlng=en It is well recognized that electromagnetic fields can affect the biological functions of living organisms at both cellular and molecular level. The potential damaging effects of electromagnetic fields and very low frequency and extremely low frequency radiation emitted by computer cathode ray tube video display monitors (VDMs) has become a concern within the scientific community. We studied the effects of occupational exposure to VDMs in 10 males and 10 females occupationally exposed to VDMs and 20 unexposed control subjects matched for age and sex. Genetic damage was assessed by examining the frequency of micronuclei in exfoliated buccal cells and the frequency of other nuclear abnormalities such as binucleated and broken egg cells. Although there were no differences regarding binucleated cells between exposed and control individuals our analysis revealed a significantly higher frequency of micronuclei (p < 0.001) and broken egg cells (p < 0.05) in individuals exposed to VDMs as compared to unexposed. We also found that the differences between individuals exposed to VDMs were significantly related to the sex of the individuals and that there was an increase in skin, central nervous system and ocular disease in the exposed individuals. These preliminary results indicate that microcomputer workers exposed to VDMs are at risk of significant cytogenetic damage and should periodically undergo biological monitoring. <![CDATA[<B>Genetic structure analysis of <I>Eufriesea violacea</I> (Hymenoptera, Apidae) populations from southern Brazilian Atlantic rainforest remnants </B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300026&lng=en&nrm=iso&tlng=en Random amplified polymorphic DNA (RAPD) markers were used to analyze the genetic structure of Eufriesea violacea populations in three fragments (85.47, 832.58 and 2800 ha) of Atlantic rainforest located in the north of the Brazilian state of Paraná. A total of twelve primers produced 206 loci, of which 129 were polymorphic (95% criterion). The proportions of polymorphic loci in each population ranged from 57.28% to 59.2%, revealing very similar levels of genetic variability in the groups of bees from each fragment. Unbiased genetic distances between groups ranged from 0.0171 to 0.0284, the smallest genetic distance occurring between bees from the two larger fragments. These results suggest that the E. violacea populations from the three fragments have maintained themselves genetically similar to native populations of this species originally present in northern Paraná. <![CDATA[<B>The Hardy-Weinberg principle </B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300027&lng=en&nrm=iso&tlng=en Hardy-Weinberg genotypic proportions can be maintained in a population under non-random mating. A compact formula gives the proportions of mating pair types. These are illustrated by some simple examples. <![CDATA[<B>ERRATUM</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572005000300028&lng=en&nrm=iso&tlng=en Hardy-Weinberg genotypic proportions can be maintained in a population under non-random mating. A compact formula gives the proportions of mating pair types. These are illustrated by some simple examples.