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Chromosome evolution in treehole breeding Anopheles (Diptera, Culicidae)
No full textThe cytogenetic profile of two Nearctic and one Paleartic treehole mosquitoes belonging to the Coelodiazesis group, Anopheles barberi, Anopheles judithae, and Anopheles plumbeus, was outlined by means of standard banding techniques and in situ hybridization. Results indicate that, during the evolution of this species group, several rearrangements have occurred including inversions, translocations, and loss of heterochromatic material and rRNA genes copy number. The karyotype of A. barberi is markedly different from the other two species, in spite of morphological similarities with the other North American species, A. judithae. This latter species has retained part of a more ancestral karyotype still shared with the Paleartic A. plumbeus. Chromosomal repatterning in A. barberi has probably facilitated isolation and divergence of the two Nearctic species, impairing introgressive hybridization with A. judithae
Le zanzare in Sardegna.III Distribuzione stagionale e abbondanza relativa nella zona di Cagliari
No full textRestriction endonuclease digestion and chromosome banding in the mosquito Culiseta longiareolata
No full textThe sibling species Anopheles atroparvus and Anopheles labranchiae are cytogenetically almost indistinguishable. The chromosome complement (2n = 6) consists of two pairs of autosomes and two heteromorphic sex chromosomes with largely homologous heterochromatic long arms. Treatment of chromosome preparations with the restriction endonucleases, Alu I, Hae III, Mbo I, Hpa II, revealed species-specific differences of the sex chromosome banding pattern. These differences involved both amount and location of digested heterochromatin. Heterochromatin heterogeneity and a high level of intraspecific polymorphism, undetected with standard banding techniques, were observed in both species. Quantitative heterochromatin differences between the sex chromosomes did not inhibit their pairing and chiasmata formation. The endonuclease Msp I, which cleaves the same target sequence as Hpa II, did not digest heterochromatic as well as euchromatic regions in both species: inhibition of cleavage by methylation of the target sequence or limited access of the enzyme to the target could be involved in this response
Chromosome banding homologies in three species of aedes (Stegomyia)
No full textThe chromosome complements of the mosquitoes Aedes aegypti, Aedes mascarensis, and Aedes albopictus, belonging to the subgenus Stegomyia, gave a uniform response to the Q-, H-, and R-banding techniques. Of the three homomorphic chromosome pairs, only the shortest or sex pair (I) showed a consistent banding pattern. In the three species, a bright yellow intercalary band was present on one arm of both chromosomes of the sex pair after heat treatment and staining with acridine orange. The rest of the chromosome and the other two pairs fluoresced orange-red. The same intercalary region appeared completely dark with the fluorochromes quinacrine and Hoechst 33258, while the rest of the chromosomes fluoresced dull. The same banding pattern was present in males and females. Size variations of the Q- and H-negative and R-positive intercalary bands were observed within each species. The results are interpreted in terms of structural homology of the sex-determining chromosomes, which is retained within the subgenus
Cytogenetic and isozyme profile of Sabethes cyaneus: a mosquito of the neo-tropical canopy
No full textSabethes cyaneus, a newly colonized culicine mosquito from the Panamanian forest canopy, has a distribution range from Honduras to Argentina. Cytogenetic studies, the first on any Sabethes species, revealed a karyotype of three pairs of homomorphic chromosomes (2n = 6). Well-developed polytene chromosomes were discovered in the larval salivary glands and a photomap standard was constructed. Clear banding patterns and consistent landmarks distinguished each of the six arms. Substantial asynapsis occurred in the three polytene chromosomes, although the banding pattern of the homologous regions appeared homosequential. A nucleolar organizer was localized in region 5A of the shortest chromosome by the recurrent association of this region with the nucleolus. The large band in region 5A was found heterozygous for width and a deletion. Additional, less conspicuous, polymorphisms for band width and staining intensity were distributed throughout the genome. Biochemical studies of 31 enzyme loci revealed 10 loci to be polymorphic, with an average heterozygosity of 13 percent. Differential expression in developmental stages occurred for 11 loci involving six enzyme
Identification of chromosome markers in interphase nuclei
No full textThe chromosome complement of the mosquito Culiseta longiareolata (2n=6) reveals distinguishable centromeric regions and one telomere of the Y chromosome by using light-induced differentiation and autoradiographic techniques in mitotic and premeiotic interphase nuclei. The localization of these cytological markers and their spatial relationships appear to be very similar in the two types of nuclei and suggest an interphase arrangement where centromeric regions are clustered together in a chromocenter like structure, close to the nuclear membrane, with the telomeres lying on the opposite pole of the nucleus
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