Resumo em Inglês:

The distribution of b-globin gene haplotypes was studied in 209 Amerindians from eight tribes of the Brazilian Amazon: Asurini from Xingú, Awá-Guajá, Parakanã, Urubú-Kaapór, Zoé, Kayapó (Xikrin from the Bacajá village), Katuena, and Tiriyó. Nine different haplotypes were found, two of which (n. 11 and 13) had not been previously identified in Brazilian indigenous populations. Haplotype 2 (+ - - - -) was the most common in all groups studied, with frequencies varying from 70% to 100%, followed by haplotype 6 (- + + - +), with frequencies between 7% and 18%. The frequency distribution of the b-globin gene haplotypes in the eighteen Brazilian Amerindian populations studied to date is characterized by a reduced number of haplotypes (average of 3.5) and low levels of heterozygosity and intrapopulational differentiation, with a single clearly predominant haplotype in most tribes (haplotype 2). The Parakanã, Urubú-Kaapór, Tiriyó and Xavante tribes constitute exceptions, presenting at least four haplotypes with relatively high frequencies. The closest genetic relationships were observed between the Brazilian and the Colombian Amerindians (Wayuu, Kamsa and Inga), and, to a lesser extent, with the Huichol of Mexico. North-American Amerindians are more differentiated and clearly separated from all other tribes, except the Xavante, from Brazil, and the Mapuche, from Argentina. A restricted pool of ancestral haplotypes may explain the low diversity observed among most present-day Brazilian and Colombian Amerindian groups, while interethnic admixture could be the most important factor to explain the high number of haplotypes and high levels of diversity observed in some South-American and most North-American tribes.

Resumo em Inglês:

The allele frequency distributions of three VNTR (D1S80, APOB and D4S43) and three STR (vW1, F13A1 and DYS19) loci were investigated in two Afro-Brazilian populations from the Amazon: Curiau and Pacoval. Exact tests for population differentiation revealed significant differences in allele frequency between populations only for the D1S80 and APOB loci. A statistically significant deviation from the Hardy-Weinberg equilibrium was observed only in the D1S80 locus of the Pacoval sample. A neighbor-joining tree was constructed based on DA genetic distances of allele frequencies in four Afro-Brazilian populations from the Amazon (Pacoval, Curiau, Trombetas, and Cametá), along with those from Congo, Cameroon, Brazilian Amerindians, and Europeans. This analysis revealed the usefulness of these Amp-FLPs for population studies - African and African-derived populations were closely grouped, and clearly separated from Amerindians and Europeans. Estimates of admixture components based on the gene identity method revealed the prevalence of the African component in both populations studied, amounting to 51% in Pacoval, and to 43% in Curiau. The Amerindian component was also important in both populations (37% in Pacoval, and 24% in Curiau). The European component reached 33% in Curiau.

Resumo em Inglês:

CCR2 is a member of the superfamily of seven transmembrane domain G protein-coupled receptors, the largest receptor superfamily in the human genome. CCR2 acts as a receptor for MCP-1 (CC chemokine) and as a co-receptor for HIV-1 cell-target entry. The gene encoding this receptor is mapped to the chromosome band 3p21. A G-to-A transition at position 190 characterizes the CCR2-64I mutation, causing valine to isoleucine substitution in codon 64. This mutation has been identified as an important factor for delaying progression to AIDS. Here, we determined the prevalence of this allele in three different Brazilian populations: 261 Amerindians inhabiting an isolated region in northern Brazil (82 samples from the Waiampi tribe, and 179 samples from the Tiriyó tribe); 89 German descendents from Joinville, a city in southern Brazil; and 305 individuals of predominantly African ancestry, from Salvador, a city in northeast Brazil. The CCR2-64I mutant allele was identified in 26% of the Tiryió and 30% of Waiampi samples, in 18% of the Joinville samples, and in 14% of the Salvador samples.

Resumo em Inglês:

A retrospective study was carried out on a sample consisting of 89,491 deliveries occurred from 1979 through 1998, in the city of São Paulo, SP, Brazil. These deliveries included 935 twin and 26 triplet births. The mean incidence per 1,000 deliveries was estimated at 10.45 for twins (5.34 for dizygotic and 5.11 for monozygotic twins) and 0.29 for triplets. The average maternal age increased significantly during this period for both twins and singletons. The temporal variation in years significantly influenced the increase of monozygotic twins and of triplets. Temporal variation and maternal age significantly influenced the dizygotic twinning rate increase. An increased proportion of monozygotic twins born to mothers aged 31 - 35 years was also detected.

Resumo em Inglês:

The Philadelphia chromosome is observed in 5% of pediatric acute lymphocytic leukemia (ALL) and in 25% to 50% of adult ALL cases, and is associated with poor prognosis. Double Ph in a hyperdiploid karyotype is common in chronic myeloid leukemia (CML), but rarely found in ALL. We report here the case of a girl diagnosed with ALL at 7 years of age. After treatment with the pediatric protocol BFM 83 for ALL, she stayed in continuous complete remission for nine years. At age 19, she was re-admitted with a white blood cell count of 6.8 x 10(9)/L with 3% blasts, and a platelet count of 65 x 109/L. Bone marrow aspirate showed 92.6% lymphoid blast cells, and chromosome analysis after G-banding revealed the karyotype 51,XX,+?5,t(9;22)(q34.1;q11.2),+16,+20,+21,+der(22)t(9;22)(q34.1;q11.2) [10]/46,XX[1]. FISH analysis for the BCR/ABL fusion showed 56% of interphase cells with two fusion signals, 30% with one, and 6% with three. Double Ph is rare in relapsed leukemia, and the possibility of secondary leukemia cannot be ruled out.

Resumo em Inglês:

This is the first time the karyotype of the Brazilian squirrel Sciurusaestuans ingrami, with 2n = 40, is described. The karyotype of this species comprises 18 pairs of biarmed and one minute pair of acrocentric autosomes, a medium-sized submetacentric X and a medium-sized acrocentric Y. Four pairs have an interstitial secondary constriction, co-located with nucleolar organizer regions (NORs), identified by silver-staining technique and fluorescent in situ hybridization (FISH) with ribosomal 18S/28S probes. The occurrence of multiple interstitial NORs is rare in rodents, and this is one of the few examples, identified by a molecular cytogenetics approach.

Resumo em Inglês:

The objective of this work was to identify QTLs for liveweight in a candidate region of bovine chromosome 5. Half-sib families from two lines, one traditional and the other new, of Canchim beef cattle (5/8 Charolais + 3/8 Zebu) were genotyped for four microsatellite markers, including the microsatellite in the IGF-1 (insulin-like growth factor-1) promoter region. Significant differences in allele distribution between the two lines were found for three markers. Interval mapping analyses in this region indicated the presence of a QTL controlling birth weight (p < 0.05) and of a QTL influencing breeding value for yearling weight (p < 0.01) in the newer line of the breed. The previously identified interaction between the IGF-1 genotype and genetic group strengthens the hypothesis of a linked QTL rather than an IGF-1 effect on growth traits in the Canchim cattle.

Resumo em Inglês:

Clean wool colour (CWC) is an important wool price determinant and has been related to suint characteristics, i.e. sudoriparous and sebaceous gland secretions, such as suint percentage and suint K content. In this work heritability, phenotypic and genetic correlations among wool colour and skin traits were examined. The genetic estimates were assessed by Restricted Maximum Likelihood (REML) procedures using average information algorithm (AIREML) in a Corriedale flock. The traits analysed were wool colour traits (CWC), yellow predictive colour (YPC), and Visual Score; suint traits such as suint percentage and potassium and sodium concentrations in suint, and physiological traits such as potassium and sodium concentrations in the skin, including plasma and red blood cells. The objectives of this study were to assess phenotypic and genetic correlations between wool colour and skin traits, and to find the suitability of these traits as indirect selection criteria for clean wool colour. Suint traits were highly genetically correlated to YPC. Suint K, but not suint percentage, was found to have a high genetic correlation with CWC. Skin K, Visual Score, YPC and suint K were amongst the best indirect selection criteria for clean wool colour. However, selection using these traits was expected to reduce CWC from 52% to 49% of that estimated under direct selection.

Resumo em Inglês:

The promoter region and the beginning of the coding region of the hsp70 stress gene were analysed in broiler chickens of a commercial breed (Hubbard-Pettersen), a breed selected for weight gain (PP1) and a non-selected breed (naked-neck Label Rouge). The naked neck gene (Naked neck, Na), which reduces feathering in birds and is thus related to heat resistance, was present in both PP1 and Label Rouge breeds. Genomic DNA was restricted with PstI and Southern blotting analysis of the samples revealed the absence of polymorphic sites for that enzyme in the promoter region and beginning of the coding region of the hsp70 gene of studied birds. PCR-SSCP analysis of these regions, however, indicated the presence of polymorphisms in the beginning of the coding region and the sequencing of the PCR products confirmed and identified two polymorphic sites in this region: a transition A ® G in position +258 and a transversion C ® G in position +276. Both mutations were considered to be silent, since they did not modify the aminoacid sequence of the protein Hsp70. The promoter region of the hsp70 gene was identical in all studied birds, indicating that the regulation pattern of this gene must be the same in all birds at the promoter region. Three different alleles (hsp70-1, hsp70-2 and hsp70-3) were identified for the hsp70 gene from the observed mutations. The allele hsp70-3 was detected in only two breeds, Hubbard-Pettersen and PP1, but at a low frequency (0,016 and 0,006, respectively).

Resumo em Inglês:

Neotropical parrots are among the most threatened groups of birds in the world, and many species are facing extinction in a near future. At the same time, the taxonomic position of many species remains unclear. Karyotype analysis has been used to elucidate the phylogenetic status of many bird groups, also providing important information for both in situ and ex situ conservation plans. The objective of the present study was to describe for the first time the karyotypes of the endangered Hyacinth Macaw, Anodorhynchus hyacinthinus, and of the Hawk-headed Parrot, Deroptyus accipitrinus. A diploid number of 2n = 70 and a karyotype similar to the main pattern previously found for the genera Ara, Cyanopsitta, Aratinga, Propyrrhura, Pionites, Pionopsitta, Nandayus, and Guaruba were found for both species. These karyotype descriptions can be a starting point for the genetic monitoring of these two declining species.

Resumo em Inglês:

Specimens of Bufo ictericus, Bufo paracnemis and a third type, considered an intermediate subgroup between these species, were cytogenetically studied by conventional Giemsa staining, C-banding and staining of the nucleolus organizer region (NOR). The nuclear DNA content and seroproteins were also analyzed to characterize these species, and verify the possibility of hybridization between them. Karyotypes and cytogenetic markers were essentially equal on the basis of the methods used. The DNA nuclear content found was 6.25 ± 0.30 pg/DNA in Bufo ictericus; 7.57 ± 0.40 pg/DNA in Bufo paracnemis and 7.04 ± 0.29 pg/DNA in the intermediate subgroup. Eletrophoresis of total blood serum in Bufo ictericus, Bufo paracnemis and the intermediate specimens revealed a remarkable difference in the patterns of the protein bands whose molecular weight corresponded to that of albumin. While the parental species presented two different bands, the intermediate form presented 4. However, only three of these bands were seen in each specimen. The results obtained pointed to a high probability for natural hybridization between Bufo ictericus and Bufo paracnemis in the site and specimens studied.

Resumo em Inglês:

The GH (growth hormone) cDNA sequence of the marine silverside fish Odontesthes argentinensis was obtained using the RACE protocol (Rapid Amplification of cDNA Ends). The marine silverside GH cDNA sequence is 928 nucleotides long and was found to encode a polypeptide of 204 amino acids, including a signal peptide of 17 amino acids. The 5' and 3' untranslated regions of the messenger are 109 and 204 nucleotides long, respectively. The deduced GH amino acid sequence was used to infer a phylogenetic tree with GH amino acid sequences from representative species belonging to the Euteleostei Subdivision using the maximum parsimony method. The topology found is according to the major phylogenetic grouping of euteleosts. The results corroborate the hypothesis that atherinids are not related to paracanthopterygians as previously suggested, and show a lack of solid synapomorphies among most of the Acanthopterygii Orders analysed indicating a complex assemblage of fishes in which the phylogenetic tree remains indeterminable.

Resumo em Inglês:

Pimelodus maculatus populations from the Tietê and Paranapanema rivers were sampled and had their genetic structure analyzed by using RAPD markers, with the aim of contributing to future conservation studies. The proportion of polymorphic loci was greater than 50% in the populations of both rivers. Genetic diversity data showed that, in spite of its nine hydroelectric plants, the Tietê river population was genetically homogeneous, whereas the Paranapanema river population was structured. This might be due to the presence of high waterfalls distributed all along its course. These data may serve as indicators for future conservation studies on the Tietê and Paranapanema rivers.

Resumo em Inglês:

Cytogenetic analysis based on the distribution of C-bands showed two groups of karyotypes in a Trypoxylon nitidum population from the Rio Doce Park, State of Minas Gerais, Brazil. One of these groups, that was identical to a previously described karyotype (n = 15; 2n = 30), had a stable chromosome number and was rich in acrocentric chromosomes, whereas the other had a variable chromosome number (n = 12 to 14; 2n = 25 to 28) and was rich in pseudo-acrocentric chromosomes. We propose a hypothesis explaining the dynamics of the modifications which occurred in the karyotype of this species, based on the minimum interaction theory of Imai et al. (1986, 1988, 1994) and on the chromosome rearrangements and heteromorphisms observed by us.

Resumo em Inglês:

Eleven Hevea brasiliensis clones were evaluated for clonal stability of latex yield. A randomized complete block design was used with four replicates, two locations, seven years and three periods per year. Stability analysis was based on clone x year and clone x year x location interactions. Five stability parameters viz environmental variance, shukla's stability variance, regression of clonal latex yield on environmental index, variance due to regression and variance due to deviation from regression were applied. There was significant clone x environment effect at the two levels of interaction. Among the eleven clones, C 162 was outstanding for clonal stability and it can serve as donor parent for stability alleles. Three clones (C 76, C 150 and C 154) were also stable. The four stable clones (C 76, C 150, C 154 and C 162) are suitable for broad-spectrum recommendation for latex yield. Five clones (C 83, C 143, C 163, C 202 and RRIM 600) will require environment-specific recommendation because of their unstable phenotype. The stability feature of two clones (C 145 and C 159) was not clear and this will be investigated in subsequent studies.

Resumo em Inglês:

Inter-simple sequence repeat (ISSR) markers were used to evaluate genetic divergence among eight Coffea species and to identify the parentage of six interspecific hybrids. A total of 14 primers which contained different simple sequence repeats (SSR) were used as single primers or combined in pairs and tested for PCR amplifications. Two hundred and thirty highly reproducible fragments were amplified, which were then used to estimate the genetic similarity and to cluster the Coffea species and hybrids. High levels of interspecific genetic variation were revealed. The dinucleotide motif (GA)9T combined with other di- tri- and tetra-nucleotides produced a greater number of DNA fragments, mostly polymorphics, suggesting a high frequency of the poly GA microsatellite motifs in the Coffea genomes. The genetic similarity ranged from 0.25 between C. racemosa and C. liberica var. dewevrei to 0.86 between C. arabica var. arabica and Hybrid N. 2. The C. arabica species shared most of its markers with five of the six hybrids suggesting that it is the most likely candidate as one of the progenitors of those hybrids. These results revealed that ISSR markers could be efficiently used for genetic differentiation of the Coffea species and to identify the parentage of Coffea interspecific hybrids.

Resumo em Inglês:

The RAPD technique associated with restriction digestion of genomic DNA was used to assess the genetic variability within and among nine populations of Coffea arabica, including six progenies belonging to the Sarchimor germplasm, the progeny PR 77054-40-10 (Catuaí Vermelho IAC 81 x Icatu), and two commercial cultivars (IAPAR 59 and Catuaí Vermelho IAC-81). These populations were evaluated using analysis of molecular variance (AMOVA), genetic similarity among progenies, and percentage of polymorphic loci. A total of 99 RAPD markers were evaluated of which 67 (67.67%) were polymorphic. AMOVA showed that 38.5% and 61.5% of the genetic variation was distributed among and within populations, respectively. The fixation index (F ST) of the genotypes was 0.385. The mean genetic variability estimated within populations ranged from 15.58 (IAPAR 59) to 8.27 (Catuaí Vermelho IAC 81). A distinct level of genetic variability was revealed for each of the coffee progenies and varieties studied. The methodology used in this investigation was useful to determine the genetic variability within and among C. arabica L. populations providing significant information for coffee breeding.

Resumo em Inglês:

The isolation of (GA)n microsatellites using a highly microsatellite-enriched library is described for the first time in common bean (Phaseolus vulgaris L.). A relatively simple and effective method to isolate DNA repeats from microsatellite-enriched libraries based on hybridization-capture of repeat regions using biotin-conjugated oligonucleotids and non-radioactive colony hybridization was carried out. PCR products from 200 to 800 bp were obtained and cloned. Of the 60 clones sequenced, 21 yielded (GA)n microsatellites with n values equal or higher than six. These (GA)n microsatellite-containing loci could be useful for further genetic mapping studies. A (GA)n microsatellite linked to a putative MADS-box gene was identified. This sequence, which represents the first MADS-box locus described to date in common bean, showed a very high similarity with other known MADS-box sequences and was grouped within the AGL2 subfamily cluster of the Arabidopsis MADS-box genes. The vicinity of microsatellites to some genes is also discussed.

Resumo em Inglês:

In order to verify whether genetic distance (GD) is associated with population mean (PM), genetic variance (GV) and the proportion of superior progenies generated by each cross in advanced generations of selfing (PS), the genetic distances between eight soybean lines (five adapted and three non-adapted) were estimated using 213 polymorphic RAPD markers. The genetic distances were partitioned according to Griffing's Model I Method 4 for diallel analysis, i.e., GDij = GD+ GGDi+ GGDj + SGDij. Phenotypic data were recorded for seed yield and plant height for 25 out of 28 populations of a diallel set derived from the eight soybean lines and evaluated from F2:8 to F2:11 generations. No significant correlation for seed yield was detected between GD and GV, while negative correlations were detected between GD and PM and between GD and PS (r = -0.74** and -0.75**, respectively). Similar results were observed for the correlation between GGDi + GGDj and PM and between GGDi + GGDj and PS (r = -0.78** and -0.80**, respectively). No significant correlation was detected for plant height. The magnitudes of the correlations for seed yield were high enough to allow predictions of the potential of the populations based on RAPD markers.

Resumo em Inglês:

Eleven samples of wheat (Triticum aestivum) from different Brazilian cultivars and six American varieties were compared for polymorphism, using primers for nine different STR loci. STR analysis of DNA from single grains of the Brazilian varieties showed that for most loci there was very little intra-cultivar polymorphism. The polymorphic variation observed for Brazilian cultivars was similar to that seen in the American varieties. For the Brazilian cultivars PCR analysis could be performed on only one half of a grain. The American samples required more seeds for analysis. The nucleotide sequences of five amplified microsatellites selected at random from the Brazilian samples were also determined and compared to those of the Chinese Spring variety. Although generally the dinucleotide sequence repeat was preserved for most loci, there were significant differences in sequences interspersed within the repeat domain. This result suggested that it may be possible to unequivocally identify the geographical origin of the cultivar by inspection of the DNA sequences of the repeat region.

Resumo em Inglês:

A modified reciprocal recurrent selection (RRS) method, which employed one cycle of high-intensity selection, was applied to two tropical maize (Zea mays L.) populations, BR-105 and BR-106, originating the improved synthetics IG-3 and IG-4, respectively. In the present study the effects of this kind of selection on the genetic structure of these populations and their synthetics were investigated at 30 microsatellite (SSR) loci. A total of 125 alleles were revealed. A reduction in the number of alleles was observed after selection, as well as changes in allele frequencies. In nearly 13% (BR-105) and 7% (BR-106) of the loci evaluated, the changes in allele frequencies were not explained, exclusively due to the effects of genetic drift. The effective population sizes estimated for the synthetics using 30 SSR loci were similar to those theoretically expected after selection. The genetic differentiation (G ST) between the synthetics increased to 77% compared with the original populations. The estimated R ST values, a genetic differentiation measure proper for microsatellite data, were similar to those obtained for G ST. Despite the high level of selection applied, the total gene diversity found in the synthetics allows them to be used in a new RRS cycle.

Resumo em Inglês:

This paper compiles results of chromosome counts of Paspalum hydrophilum, P. modestum and P. palustre. Four Brazilian accessions of P. modestum have shown 2n = 2x = 20 chromosomes, a number already found in one accession from Argentina and in two from Brazil. Three other Brazilian accessions showed tetraploid level (2n = 4x = 40), which was previously unknown in this species. In P. hydrophilum, only one of the accessions analyzed presented tetraploid level, initially established for the species from plants collected in Argentina. Five additional accessions from Brazil showed the diploid number, previously detected in a single Brazilian population. A tetraploid cytotype was found in P. palustre, previously known as a diploid species. In addition to confirming the occurrence of distinct ploidy levels for all three species, the results establish the predominance of the diploid level in P. hydrophilum and P. modestum accessions collected in Brazil.

Resumo em Inglês:

The chromosome number of 14 accessions of Bromus auleticus Trin. ex Nees, native of Rio Grande do Sul, was 2n = 6x = 42, same ploidy level found in other South-American Bromus species. Its chromosomes were metacentric or submetacentric, ranging from ca. 4 mm to ca. 8 mm in length. Up to two satellite-bearing chromosome pairs were sometimes observed. However, as already reported for other species, the high symmetry and homogeneity of the karyotypes made it difficult to detect possible intraspecific differences.

Resumo em Inglês:

The aim of this research was to study the mating system of a natural population of Theobroma grandiflorum (cupuassu) from Nova Ipixuna, Pará state, using microsatellite markers. Eight polymorphic microsatellite loci were analyzed in eight families, each represented by 10 six-month old seedlings derived from open-pollinated pods. The estimation for the multilocus outcrossing rate (<img border=0 id="_x0000_i1026" src="../../img/revistas/gmb/v26n3/a25img01.gif" align=absmiddle>m = 1.0) and individual outcrossing rate (<img border=0 id="_x0000_i1027" src="../../img/revistas/gmb/v26n3/a25img01.gif" align=absmiddle> = 1.0) for this population suggests that T. grandiflorum may be a perfect outbreeding (allogamous) species. Likewise, for the studied population the estimate for single locus outcrossing rate (<img border=0 id="_x0000_i1028" src="../../img/revistas/gmb/v26n3/a25img01.gif" align=absmiddle>S) was elevated (0.946), but lower than <img border=0 id="_x0000_i1029" src="../../img/revistas/gmb/v26n3/a25img01.gif" align=absmiddle>m, confirming the likely outcrossing character of the species and suggesting the occurrence of 5.4% biparental inbreeding rate (<img border=0 id="_x0000_i1030" src="../../img/revistas/gmb/v26n3/a25img01.gif" align=absmiddle>m - <img border=0 id="_x0000_i1031" src="../../img/revistas/gmb/v26n3/a25img01.gif" align=absmiddle>S). The estimation of genetic divergence (<img border=0 id="_x0000_i1032" src="../../img/revistas/gmb/v26n3/a25img02.gif" align=absmiddle>st) between allelic frequencies in ovules and pollen revealed a deviation from random mating in 75% of the evaluated loci. Likewise, the estimate of correlation of paternity (<img border=0 id="_x0000_i1033" src="../../img/revistas/gmb/v26n3/a25img03.gif" align=absmiddle>P = 0.930) and the mean coefficient of co-ancestrality within families (<img border=0 id="_x0000_i1034" src="../../img/revistas/gmb/v26n3/a25img04.gif" align=absmiddle>XY = 0.501) indicated that the outcrossings were predominantly correlated, and the offspring were full-sibs. These results suggested that for this particular population of T. grandiflorum, the sampling strategy for genetic conservation and breeding should adopt specific models for families derived from correlated outcrossing (full-sibs) and not the ones usually adopted in classic outcrossing species breeding programs (half-sibs).

Resumo em Inglês:

Ethidium bromide (EB) is an intercalating inhibitor of topoisomerase II and its activities are related to chemotherapeutic drugs used in anti-cancer treatments. EB promotes several genotoxic effects in exposed cells by stabilising the DNA-enzyme complex. The recombinagenic potential of EB was evaluated in our in vivo study by the loss of heterozygosity of nutritional markers in diploid Aspergillus nidulans cells through Homozygotization Index (HI). A DNA repair mutation, uvsZ and a chromosome duplication DP (II-I) were introduced in the genome of tested cells to obtain a sensitive system for the recombinagenesis detection. EB-treated diploid cells had HI values significantly greater than the control at both concentrations (4.0 x 10-3 and 5.0 x 10-3 mM). Results indicate that the intercalating agent is potentially capable of inducing mitotic crossing-over in diploid A. nidulans cells.