title: C band variation in polytene chromosomes of Chironomus riparius (Diptera, Chironomidae) from a polluted Piedmont station (Italy).
abstract: C banding in polytene chromosomes of Chironomus riparius from a Santena polluted station of the river Po, Italy was described. A large variation in the appearance of C bands was established. The process involved the transformation of euchromatin into heterochromatin. Activation of all chromosomes at telomeres was found. A structural modification of telomeric heterochromatin may exist. The centromeric heterochromatin was rarely observed. A high percentage of an amplification (88%) in arm F, B3h, was recorded. These changes in the appearance of heterochromatin in the population studied could be considered as a type of polymorphic system, existing in the polluted population. For the first time in C. riparius two types of position effect variegation are reported. In arm E the euchromatin near to the centromere became inactive due to a heterozygous inversion and in arms D and F the opposite phenomenon was observed in which a heterozygous inversion partly suppressed the inactivation of heterochromatin.
authors.affiliation: Insitute of Zoology, Bulgarian Academy of Sciences, Tzar Osvoboditel, Sofia, Bulgaria.
authors.forename: P
authors.initials: P
authors.lastname: Michailova
authors.forename: L
authors.initials: L
authors.lastname: Ramella
authors.forename: G
authors.initials: G
authors.lastname: Sella
authors.forename: S
authors.initials: S
authors.lastname: Bovero
mesh_terms: D000818:Animals; D002683:Chironomidae / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000648:ultrastructure; D002871:Chromosome Banding; D007446:Chromosome Inversion; D002875:Chromosomes / Q000187:drug effects / Q000235:genetics / Q000648:ultrastructure*; D005786:Gene Expression Regulation; D006570:Heterochromatin / Q000235:genetics / Q000648:ultrastructure; D007558:Italy; D019216:Metals, Heavy / Q000009:adverse effects*; D012989:Soil Pollutants / Q000009:adverse effects*; D016615:Telomere / Q000648:ultrastructure
chemical_list: D006570:Heterochromatin; D019216:Metals, Heavy; D012989:Soil Pollutants