Identification of two subfamilies of micropia transposable element in species of the repleta group of Drosophila

The occurrence, number of insertion sites and antisense RNA expression of micropia transposable element were studied in 26 species that belong to three subgroups (mercatorum, mulleri and hydei) of repleta group of Drosophila. Under high specific PCR, micropia sequences were detected in 11 species, but under less stringent condition, this retrotransposon was detected in all species. The widespread distribution of micropia suggests that this element was already present at the common ancestor of the repleta group of Drosophila. Southern blot analysis showed a variation from 0 to 17 different insertion sites and the occurrence of male-specific sequences. We found that the expression of the 1.0 kb micropia antisense RNA is variable among the species and tissues (soma and testis), which suggests that more than one mechanism regulates transposition in these species. Variation of amplification by PCR and of antisense RNA expression, as well as divergence of nucleotide sequences among the species allow us to suggest that at least two subfamilies of micropia transposable element are harbored by the genome of this species group.

KARYOTYPE AND NUCLEOLUS ORGANIZER REGIONS OF PYRRHULINA CF AUSTRALIS (PISCES, CHARACIFORMES, LEBIASINIDAE)

The mitotic chromosomes and nucleolus organizer regions (NORs) of the Upper Parana Basin fish Pyrrhulina cf. australis were studied. The karyotype (2n = 40; 6st + 34a) is characterized by the presence of four chromosome pairs with NORs, one of them with NORs in both terminal regions. Comparison of this karyotype with those of other Characiformes, revealed a strong similarity to the family Erythrinidae.

CYTOGENETIC STUDIES ON FISHES OF THE FAMILY PIMELODIDAE (SILUROIDEI)

Four fish species of the family Pimelodidae were analyzed. Bergiaria westermani and two different Pimelodus species have the same diploid chromosome number (2n - 56). Despite some differences in chromosome structure, these species are highly similar in karyotype and differ from Pimelodella sp., which presents a reduction in chromosome number to 2n = 46. The data confirm the extensive chromosome variability existing in this family, characterized by intraindividual and/or population polymorphisms of a structural nature which may or may not be sexlinked, and by the presence of supernumerary chromosomes.

CYTOGENETIC AND DNA CONTENT STUDIES OF ARMORED CATFISHES OF THE GENUS CORYDORAS (PISCES, SILURIFORMES, CALLICHTHYIDAE) FROM THE SOUTHEAST COAST OF BRAZIL

Cytogenetic and DNA content studies were done on six nominal species of Corydoras from the southeast coast of Brazil. The data show that several nominal species present local populations with differences in karyotype or DNA content. There are at least two groups of Corydoras species with similar karyotypic structure in this region: the first composed by C. ehrhardti, C. nattereri and C. paleatus and the second composed of C. barbatus, C. macropterus and C. prionotos. These two groups of species are probably not derived directly from the same ancestral line. The speciation process of Corydoras species from the southeastern coast of Brazil is discussed.

HERITABILITY OF THE NUMBER OF OVARIOLES IN HONEY-BEE WORKERS (APIS-MELLIFERA L) (HYM, APIDAE)

Narrow and broad sense heritabilities (h(2)) of the number of ovarioles in Apis mellifera L. workers were estimated using two distinct data sets, based on groups of half (queens inseminated by several drones) and super-sisters (single drone insemination). The values found are in the usual range for economically important characters (0.25-0.38).

SISTER CHROMATID EXCHANGES IN HETEROZYGOTE BETA-THALASSEMIC PATIENTS WITH NORMAL FOLATE LEVELS

Lymphocytes from beta thalassaemia heterozygote patients, with normal levels of plasma folic acid cultured for 72 h in a folate rich medium, were not found to contain increased rates of sister chromatid exchanges (SCE). A wide intra and interindividual variability was found in both thalassaemic and control groups and methodological and biological factors, such as types of peripheral lymphocytes, sex, age, and smoking, alcohol and coffee drinking, as well as dietary habits, are possibly responsible for these variations.

Testing transposable elements as genetic drive mechanisms using Drosophila P element constructs as a model system

The use of transposable elements (TEs) as genetic drive mechanisms was explored using Drosophila melanogaster as a model system. Alternative strategies, employing autonomous and nonautonomous P element constructs were compared for their efficiency in driving the ry(+) allele into populations homozygous for a ry(-) allele at the genomic rosy locus. Transformed flies were introduced at 1%, 5%, and 10% starting frequencies to establish a series of populations that were monitored over the course of 40 generations, using both phenotypic and molecular assays. The transposon-borne ry(+) marker allele spread rapidly in almost all populations when introduced at 5% and 10% seed frequencies, but 1% introductions frequently failed to become established. A similar initial rapid increase in frequency of the ry(+) transposon occurred in several control populations lacking a source of transposase. Constructs carrying ry(+) markers also increased to moderate frequencies in the absence of selection on the marker. The results of Southern and in situ hybridization studies indicated a strong inverse relationship between the degree of conservation of construct integrity and transposition frequency. These finding have relevance to possible future applications of transposons as genetic drive mechanisms.

Genetic relationships between Brazilian species of Molossidae and Phyllostomidae (Chiroptera, Mammalia)

A comparative analysis of G-banded karyotypes was performed for seven species of Chiroptera, representing two families (Phyllostomidae and Molossidae). Despite the differences in diploid and fundamental numbers, extensive homologies between six karyotypes were identified: A . planirostris, P. lineatus, S. lilium, G. soricina, P. hastatus (Phyllostomidae) and M. rufus (Molossidae). Robertsonian rearrangements and pericentric inversions account for the differences between the karyotypes of phyllostomid and molossid species. The homologies and rearrangements observed reinforce the monophiletic origin of phyllostomids and the inclusion of species in different subfamilies. In situ hybridization with genomic DNA revealed considerable conservation of the karyotypes, including C. perspicillata, that did not show G-band homologies with the other species analyzed. For the first time, chromosomal evidence is presented of a common origin for Phyllostomidae and Molossidae.