1,721,025 research outputs found
Cytogenetic analysis of the second chromosome heterochromatin of Drosophila melanogaster
No full textI trasposoni. In: "Genetica" a cura di Sergio Pimpinelli.
No full textNegli eucarioti, gli elementi trasponibili rappresentano una porzione signi cativa del genoma. Gli e etti genetici a breve termine della trasposizione sono di solito deleteri, perché le mutazioni inserzionali possono alterare l’espressione dei geni. Secondo alcuni ricercatori, l’unica vera funzione degli elementi trasponibili sarebbe fornita da uno specializzato apparato
molecolare che ne garantisce la propagazione all’interno del genomi; in quest’ottica gli elementi trasponibili rappresenterebbero un particolare tipo di “DNA egoista”. Al contrario, studi più recenti indicano che nel corso dell’evoluzione gli elementi trasponibili
possono stabilire relazioni funzionali con il genoma ospite, fino ad acquisire, in alcuni casi, dei ruoli essenziali
Position effect variegation in Drosophila melanogaster relationship between suppression effect and the amount of the Y chromosome
No full textThe heterochromatic rolled gene of Drosophila melanogaster is extensively polytenized and transcriptionally active in the salivary gland chromocenter.
No full textFluorescent in situ hybridization with transposable element probes to mitotic chromosome heterochromatin of Drosophila.
No full textThe technique of in situ hybridization of DNA probes to Drosophila chromosomes has been initially applied to the salivary gland polytene chromosomes and is now routinely used for mapping single-copy and repetitive DNA sequences, such as transposable elements, to the euchromatic regions of these chromosomes. However, most of the heterochromatin normally escapes cytogenetic analyses on polytene chromosomes because it is organized in a poorly differentiated cytological structure called the chromocenter. This peculiar organization does not allow a detailed mapping of DNA clones to heterochromatin. Such a limitation can be overcome by the fluorescent in situ hybridization (FISH) technique on mitotic chromosomes of D. melanogaster, where heterochromatin has been extensively characterized by banding techniques and subdivided into several cytologically diverse regions. Digital images of FISH signals and DAPI staining can be separately recorded by CCD camera, pseudocolored, and merged using specific software for image analysis. The visualization of the signals and DAPI banding pattern on a single chromosome enables the mapping of a given sequence to specific cytological regions of mitotic heterochromatin. This method has initially proven successful in the detection and mapping of transposable element clusters in the heterochromatin of D. melanogaster and has been used to study the distribution of repeated and even single-copy sequences
I element distribution in mitotic heterochromatin of Drosophila melanogaster reactive strains: identification of a specific site which is correlated with the reactivity levels
No full textThe I factor is a Drosophila melanogaster LINElike element that efficiently transposes in the genetic system of I-R hybrid dysgenesis. It has been suggested that some of the I-related sequences located in the heterochromatin of D. melanogaster are involved in the regulation of I factor activity. In this work we have performed fluorescent in situ hybridization (FISH) mapping of I element sequences in mitotic heterochromatin of nine differentially reactive D. melanogaster strains. The results of our analysis showed that a single hybridization site mapping to region h28 of the distal heterochromatin of the X chromosome is present in three strains with low or intermediate levels of reactivity, while it is undetectable in six highly reactive strains. Together, these observations suggest a negative correlation between I sequences located at h28 and the level of reactivity. To this regard, it is intriguing that flamenco and COM, two loci that regulate the activity of D. melanogaster endogenous retroviruses also map to the distal heterochromatin of the X chromosome. Our data represent the first experimental evidence in favour of a silencing effect exerted by naturally occurring I element sequences located in pericentromeric heterochromatin
Genetic variability of heterochromatin induced by I-R dysgenesis in Drosophila melanogaster.
No full textCytogenetic analysis of segregation distortion in Drosophila melanogaster: The cytological organization of the Rsp locus
No full textRevising the selfish DNA hypothesis: new evidence on accumulation of transposable elements in heterochromatin.
No full textThe bulk of the eukaryotic genome is composed of families of repetitive sequences that are genetically silent
and exhibit various types of instability. Transposable elements (TEs) are particularly commmon in
heterochromatic regions of the genome – a location where TEs might do less damage to their host. Recent
advances suggest that the relationship between TEs and heterochromatin might not be quite so straightforward
- …
