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A S Fox

Publications and source records attributed to A S Fox.

At least 37 records · Page 2Linked to original sources
PubMed1975

Gene transfer in Drosophila melanogaster: cytological alterations in the salivary chromosomes of transformed stocks.

Cytological abnormalities are observed in salivary chromosomes of stocks of Drosophila melanogaster possessing DNA-induced, v+ transformations mapping either at 1-0.0 or 1-33.0. In initial studies, the untransformed control stock and six transformed stocks were assigned code numbers prior to cytological examination. Salivary chromosome regions 1B9 10--C 2-3 and 10A1 2--10B1-2 were carefully examined in each of the coded stocks. (Band 1B11 is tentatively identified as the site of the suppressor-of-sable locus at 1-0.0 and band 10A1 is the site of the vermilion locus at 1-33.0.) When cytological studies were complete each of the stocks was identified. In every transformed stock examined, anomalies had been scored in association with the chromosome region corresponding to the map position of the DNA-induced alteration. In the control stock, anomalies were observed at neither position. -- Approximately 10-15% of the nuclei in transformed stocks exhibit significant departure from normality in the pertinent chromosome region. The perturbations range from minor alterations of banding pattern to apparent pieces of extra chromatin in the most extreme cases. In stocks with v+ transformations mapping at 1-33.0, apparent extra chromatin is observed with frequencies varying from 0.05 to 0.02. In these cases the abnormal structures are associated with salivary band 10A1-2, forming a band-like structure, frequently an almost perfect doublet (open or closed), often lying in an abnormal position, and with fine chromatin threads connecting to the chromosomal doublet. In stocks with v+ transformations mapping at 1-0.0, apparent extra chromatin is observed with a frequency of about 0.001. These abnormal structures are frequently thread-like, lying to the side or off the tip of the chromosome, with compact regions which sometimes resemble chromomeres, and with fine threads connecting to the chromosomal 1B11 region.

Animals↗
PubMed1973

A family of three related satellite DNAs in Drosophila virilis.

Isolated single DNA strands of satellites II or III of Drosophila virilis form hybrid duplexes with the complementary single strands of satellite I. The hybrids denature at a higher temperature than controls, renature rapidly, and form bands of hybrid density in neutral CsCl. Isolated single strands of satellite II do not form clear-cut duplexes with the complementary strands of satellite III. Mixtures of satellites II and III denature at the same temperature as controls, and do not form bands in neutral CsCl. Therefore, satellite I-II and I-III complexes are extensively base paired, while satellite II-III complexes are minimally base paired. These experiments demonstrate partial homology among the three satellites, and suggest an evolutionary relationship among them. They also suggest that satellites and other repeated sequences from related species, which do not form hybrids in vitro, could have a common evolutionary origin, but have accumulated enough base substitutions to lose interspecific homology demonstrable by hybrid duplex formation.

Animals↗
PubMed1971

DNA-induced transformation in Drosophila: genetic analysis of transformed stocks.

The exosome model of transformation in Drosophila melanogaster proposes that DNA fragments enter the cells of treated individuals and become firmly associated with their homologous chromosome segments, but are never integrated into the linear structure of the chromosome. This paper reports results that validate two central predictions of the model: (a) the introduced genetic information usually maps precisely at the site of the target locus, and (b) the original chromosomal information is still present at that site.

Animals↗
PubMed1970

DNA-induced transformation in Drosophila: locus-specificity and the establishment of transformed stocks.

The genetic changes induced in Drosophila melanogaster by DNA obtained from flies differing at specified genetic loci exhibit the general features of transformation, namely locus specificity and heritability. These properties have provided the basis for the establishment of transformed stocks. The phenomenon also exhibits striking special features, prominent among which is the observation that transformed individuals are always mosaics and that whole-body transformants are absent even in established stocks. The exosome model (which proposes that DNA segments enter the cells of treated individuals and become firmly associated with their homologous chromosome segments, but are never integrated into the linear structure of the chromosome) is formulated to fit these observations.

Animals↗
PubMed1970

DNA-induced transformation in Drosophila: evidence for transmission without integration.

A key feature of the exosome model of transformation in Drosophila melanogaster is that the DNA segments responsible for the phenomenon are not integrated into the linear structure of the chromosomes. This feature is confirmed by the failure to find whole-body transformants in a series of large-scale experiments, and by the absence of evidence for integration under conditions favoring genetic exchange between chromosomes and introduced DNA.

Animals↗