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At least 91 records · Page 5Linked to original sources
PubMed1979

DNA sequence of the transposable element IS1.

The nucleotide sequence of an IS1 element recently transposed into the lacI gene is reported. This sequence is nearly identical to one previously reported for another IS1 element (Ohtsubo and Ohtsubo, 1978). The implications of this similarity are discussed. The sizes of potential polypeptides encoded in the IS1 DNA have been determined and possible roles for these peptides in the illegitimate recombination events mediated by the element are considered.

Bacterial Proteins↗
PubMed1986

Variegated expression of the Sgs-4 locus in Drosophila melanogaster.

Experiments on T(1;4)wm258-21 larvae of Drosophila melanogaster are described which establish the existence of a salivary gland specific marker for position-effect variegation. The marker is a glue protein gene called Sgs-4 which is expressed during the third larval instar. Using temperature as a variegation modifier, we showed that cytological compaction for the Sgs-4 chromosomal locus is enhanced at 17 degrees C and reduced at 29 degrees C. We also found that the Sgs-4 protein and transcript from salivary glands at 17 degrees C accumulate to roughly half the levels found in salivary glands at 29 degrees C. Southern analysis suggested that the Sgs-4 locus at 17 degrees C is polytenized to roughly one-third the level at 29 degrees C. The results are discussed with respect to alternative models of variegation.

DNA↗
PubMed1975

The human leulocyte test system. VII. Further investigations concerning micronucleus-derived premature chromosome condensation.

Premature chromosome condensation (PCC) from X-ray induced micronuclei shows a dose-effect relationship in human leukocytes in vitro. Preparations at different culture times without colcemide treatment reveal complex variations of the frequencies of micronuclei and PCC correlated with the fixation time. The positions of PCC patches in the metaphase plate and the frequencies of different PCC types (S and G2) ar independent on the X-ray dose. The latter indicates that the slowing down of the micronuclei in the cell cycle, which is the reason for the formation of PCC, may be an outcome rather of a regulatory phenomenon than of an unspecific physiological damage of the chromatin included in the micronuclei. This is especially evident from labeling experiments with tritiated thymidine, showing that the extent of asynchrony between main nuclei and micronuclei is independent on the X-ray dose. Labeling experiments with tritiated uridine reveal a X-ray dose dependent suppression of RNA synthesis in cells with main nuclei and micronuclei. THE S-phase nature of "pulverized" PCC patches could be verified by incorporation of tritiated thymidine in aound 50%. Staining of centromeric heterochromatin in micronuclei reveal a frequency of micronuclei with centromeric heterochromatin resembling the frequency of G2-phase PCC found in mitoses.

Cell Nucleus↗
PubMed1981

Isolation of dominant suppressor mutations for position-effect variegation in Drosophila melanogaster.

Dominant suppressor mutations for position-effect variegation have been isolated by using a strongly variegated line carrying the wm4 chromosome (wm4h) and the dominant enhancer mutant En(var)c101. The use of an effective genetic test system made it possible to isolate more than 100 strongly dominant suppressor mutations for position-effect variegation. This suggests that the phenomenon of position-effect variegation is characterised by a complex genetic basis. The significance of the isolated mutants to genetic dissection of structural and regulatory functions of the eukaryotic chromosome is discussed.

Animals↗
PubMed1989

Isolation of the facA (acetyl-coenzyme A synthetase) and acuE (malate synthase) genes of Aspergillus nidulans.

Acetate inducible genes of Aspergillus nidulans were cloned via differential hybridization to cDNA probes. Using transformation of mutant strains the genes were identified as facA (acetyl-Coenzyme A synthetase) and acuE (malate synthase). The levels of RNA encoded by these genes were shown to be acetate inducible and subject to carbon catabolite repression. Induction is abolished in a facB mutant and carbon catabolite repression is relieved in a creA mutant.

Acetate-CoA Ligase↗
PubMed1988

Localisation of several chromosome I genes of Aspergillus nidulans: implications for mitotic recombination.

Another laboratory previously reported that the vast majority of mitotic recombinants in chromosome I disomics of Aspergillus nidulans arise from double exchange events involving the centromeric region and a far distal, possibly telomeric, region. This conclusion was based on the assumption that the camC gene is located in a position far distal to the centromere on the left arm of chromosome I. As a left arm location for camC distal to the centromere was possibly in conflict with mapping data obtained in the context of an unrelated project, camC was partially mapped along with three other previously unlocated chromosome I genes, davA, ornD and uapA. The data presented here indicate that camC is located in a position far distal to the centromere but on the right arm of chromosome I, a conclusion also supported by the previous data. The positioning of uapA and camC in far distal locations on the right arm of chromosome I indicates the existence of a vast, otherwise nearly unmapped region on this chromosome arm.

Aspergillus nidulans↗
PubMed1995

Cytogenetics of an intrachromosomal transposition in Neurospora.

Knowledge of intrachromosomal transpositions has until now been primarily cytological and has been limited to Drosophila and to humans, in both of which segmental shifts can be recognized by altered banding patterns. There has been little genetic information. In this study, we describe the genetic and cytogenetic properties of a transposition in Neurospora crassa. In Tp(IR-->IL)T54M94, a 20 map unit segment of linkage group I has been excised from its normal position and inserted near the centromere in the opposite arm, in inverted order. In crosses heterozygous for the transposition, about one-fifth of surviving progeny are duplications carrying the transposed segment in both positions. These result from crossing over in the interstitial region. There is no corresponding class of progeny duplicated for the interstitial segment. The duplication strains are barren in test crosses. A complementary deficiency class is represented by unpigmented, inviable ascospores. Extent of the duplication was determined by duplication-coverage tests. Orientation of the transposed segment was determined using Tp x Tp crosses heterozygous for markers inside and outside the transposed segment, and position of the insertion relative to the centromere was established using quasi-ordered half-tetrads from crosses x Spore killer. Quelling was observed in the primary transformants that were used to introduce a critical marker into the transposed segment by repeat-induced point mutation (RIP).

Centromere↗