The C-staining method and four G-staining methods induce, on newt chromosomes, the formation of darkly stained bands, whose distribution patterns are typical for each species studied so far (Triturus alpastris apuanus, T. cristatus carnifex, T. italicus, T. marmoratus marmoratus, T. vulgaris meridionalis). The localization of C- and G- bands appears to be identical within a specific karyotype. Also the Q- staining method induces bands on Triturus chromosomes, but their brilliance greatly increases after treatment with a denaturation-renaturation process; however the nucleolus-organizing regions, which do not stain by Giemsa, show no fluorescence and the heteromorphic region of sex chromosomes, which darkly stains by Giemsa shows pale fluorescence even when the cytological preparations are previously submitted to the denaturation-renaturation process. Evidence is supplied supporting the hypothesis of the coincidence rather than of the contiguity between the bands obtained by the Giemsa stain and those visible after use of the alkylating fluorochrome quinacrine. Therefore, in each newt species studied in the present work, the banding pattern seems to be unique for C-, G- and Q- bands. Keeping in mind that these bands are often identified as to some heterochromatic tracts which appear after cold treatment, the opportunity has been taken into account to study also the DNA replication at those levels, using $\sideset{^3}{}{\operatorname{H}}$-thymidine and autoradiographic technique. At present, the results obtained so far seem to point out that most of the bands may correspond to chromosome regions characterized by a late replication process.
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Con il contributo del Ministero per i Beni e le Attività Culturali