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  • 1
    Electronic Resource
    Electronic Resource
    Mutations in somePolycomb group genes ofDrosophila interfere with regulation of segmentation genes (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 474-483 
    Details
    ISSN: 1617-4623
    Keywords: Polycomb group ; Segmentation genes ; Drosophila melanogaster ; Central nervous system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mutations in severalPolycomb (Pc) group genes cause maternal-effect or zygotic segmentation defects, suggesting thatPc group genes may regulate the segmentation genes ofDrosophila. We show that individuals doubly heterozygous for mutations inpolyhomeotic and six otherPc group genes show gap, pair rule, and segment polarity segmentation defects. We examined double heterozygous combinations ofPc group and segmentation mutations for enhancement of adult and embryonic segmentation defects.Posterior sex combs andpolyhomeotic interact withKrüppel 2 and enhance embryonic phenotypes ofhunchback andknirps, andpolyhomeotic enhanceseven-skipped. Surprisingly, flies carrying duplications ofextra sex combs (esc), that were heterozygous for mutations ofeven-skipped (eve), were extremely subvital. Embryos and surviving adults of this genotype showed strong segmentation defects in even-numbered segments. Antibody studies confirm that expression ofeve is suppressed by duplications ofesc. However,esc duplications have no effect on other gap or pair rule genes tested. To our knowledge, this is only the second triplo-abnormal phenotype associated withPc group genes. Duplications of nine otherPc group genes have no detectable effect oneve. Expression ofengrailed (en) was abnormal in the central nervous systems of mostPc group mutants. These results support a role forPc genes in regulation of some segmentation genes, and suggest thatesc may act differently from otherPc group genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00583898
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  • 2
    Electronic Resource
    Electronic Resource
    Genes which suppress position-effect variegation in Drosophila melanogaster are clustered (1983)
    Springer
    Molecular genetics and genomics 191 (1983), S. 326-333 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have isolated more than 50 dominant suppressors and 3 dominant enhancers of position effect variegation in Drosophila melanogaster. To our surprise, genetic mapping studies revealed that the Su(var) mutations are not randomly dispersed throughout the genome of this organism. Rather they fall into very discrete clusters. Moreover, all of the induced Su(var) mutations which map to a major second chromosome cluster are recessive lethal, whereas all of those which map within any of several third chromosome clusters are viable. Complementation analysis involving Su(var) mutations located within the 2L cluster suggests that several different loci occupy this site. Thus, these clusters may represent groupings of functionally related but distinct Su(var) loci. A subset of the suppressors were examined for their effects on several different variegating rearrangements. The results suggest that the suppressing ability of the mutants is general. Interestingly, the effects of the suppressors in males appears to be highly dependent upon the presence of the Y chromosome. Finally, examination of the Su(var) mutants at different developmental temperatures indicated that at least one of them is temperature-sensitive. These findings are discussed with respect to the potential for genetic and functional dissection of loci which encolde chromosomal components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334834
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  • 3
    Electronic Resource
    Electronic Resource
    RNA-DNA hybridization analyses of tRNA 3b Val in Drosophila melanogaster (1982)
    Springer
    Molecular genetics and genomics 185 (1982), S. 390-396 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Transfer RNA was extracted from 50–300 mg of adult flies and specifically labeled in vitro. The level of individual isoacceptors was quantitated by efficient annealing to Drosphila tRNA genes carried on recombinant DNA plasmids immobilized on nitrocellulose filters. The level of tRNA 3b Val in the tRNA isolated from flies deficient in the major tRNA 3b Val loci has been examined. The results show that deletion of the major tRNA 3b Val loci resulted in a reduction of approximately 50% in the level of tRNA 3b Val but did not produce the Minute phenotype; furthermore the effects of deficiencies at two loci were approximately additive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334129
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization of mutations that enhance position-effect variegation in Drosophila melanogaster (1989)
    Springer
    Molecular genetics and genomics 216 (1989), S. 328-333 
    Details
    ISSN: 1617-4623
    Keywords: Enhancers of position-effect variegation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Several mutants that enhance the gene inactivation associated with position-effect variegation [E(var) mutants] have been characterized. These include three ethyl methanesulfonate (EMS)-induced lesions and a second chromosome duplication. Each of the EMS mutations maps to a discrete euchromatic site on the third chromosome. One is located within the chromosomal region occupied by a cluster of Su(var) mutations. All four E(var) mutants enhance the inactivation of several different variegators and therefore they appear to influence position-effect variegation generally. However, the enhancement caused by the single site E(var) mutations is less striking than that caused by the duplication or by loss of the Y chromosome. The interaction between the E(var) mutants and selected Su(var) mutations, as well as the effects of extra Y heterochromatin on E(var) expression, have also been investigated. Based on the results of these studies, various hypothetical functions of the E(var) + products are suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334372
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  • 5
    Electronic Resource
    Electronic Resource
    Genetic interactions and dosage effects of Polycomb group genes of Drosophila (1995)
    Springer
    Molecular genetics and genomics 246 (1995), S. 291-300 
    Details
    ISSN: 1617-4623
    Keywords: Polycomb group ; trithorax group ; Homeotic ; Chromatin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Polycomb (Pc) group of genes are required for maintenance of cell determination in Drosophila melanogaster. At least 11 Pc group genes have been described and there may be up to 40; all are required for normal regulation of homeotic genes, but as a group, their phenotypes are rather diverse. It has been suggested that the products of Pc group genes might be members of a heteromeric complex that acts to regulate the chromatin structure of target loci. We examined the phenotypes of adult flies heterozygous for every pairwise combination of Pc group genes in an attempt to subdivide the Pc group functionally. The results support the idea that Additional sex combs (Asx), Pc, Polycomblike (Pcl), Posterior sex combs (Psc), Sex combs on midleg (Scm), and Sex combs extra (Sce) have similar functions in some imaginal tissues. We show genetic interactions among extra sex combs (esc) and Asx, Enhancer of Pc, Pcl, Enhancer of zeste E(z), and super sex combs and reassess the idea that most Pc group genes function independently of esc. Most duplications of Pc group genes neither exhibit anterior transformations nor suppress the extra sex comb phenotype of Pc group mutations, suggesting that not all Pc group genes behave as predicted by the mass-action model. Surprisingly, duplications of E(z) enhance homeotic phenotypes of esc mutants. Flies with increasing doses of esc + exhibit anterior transformations, but these are not enhanced by mutations in trithorax group genes. The results are discussed with respect to current models of Pc group function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00288601
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  • 6
    Electronic Resource
    Electronic Resource
    Screen for enhancers of Polycomb and Polycomblike in Drosophila melanogaster (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 15 (1994), S. 425-434 
    Details
    ISSN: 0192-253X
    Keywords: Polycomb group ; homeotic ; spalt ; devenir ; Su(Pc)37D ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: There are 11 Polycomb group genes known in Drosophila. These genes are negative regulators of homeotic gene expression, and may act by modifying chromatin structure. It is not clear how many members of the Polycomb group of genes exist. Many were discovered because of their homeotic phenotypes, or because they enhance homeotic mutations. Systematic screens for enhancers of Polycomb have identified previously known members of the Polycomb group. In an attempt to discover cytological locations of new Polycomb group genes, we crossed deletions uncovering about 20% of the genome to Polycomb-like and Polycomb and scored for enhancement of the extra sex combs phenotype. Haploidy for four regions, 36F7-37A, 43E18; 44B5-9, 70C2-6, and 70C6-15; 70D enhanced the extra sex comb phenotype associated with strong Polycomb group mutations. These regions have homeotic phenotypes either as homozygous embryos or heterozy-gous adults, or both. We also show that spalt enhances Polycomb group mutations. These results are discussed with respect to previous estimates of Polycomb group gene number. © 1994 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020150505
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