Genetic analysis of a Minute mutation in the distal region of the second chromosome of Drosophila melanogaster
TL;DR: Genetic organization of a proximal region of the second chromosome in Drosophila melanogaster has been analysed by saturation mutagenesis and seven alleles were uncovered in this region in addition to the one previously known.
Abstract: Genetic organization of a proximal region of the second chromosome inDrosophila melanogaster has been analysed by saturation mutagenesis. Seven alleles were uncovered in this region in addition to the one previously known. Besides this, quite a few mutations were isolated that non-complemented more than one group of lethals and looked very much like deletions of varying extent. Except one, all the lethals complemented M(2)z.
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TL;DR: It is concluded that the deleterious effects of aneuploidy are mostly the consequence of the additive effects of genes that are slightly sensitive to abnormal dosage.
Abstract: By combining elements of two Y-autosome translocations with displaced autosomal breakpoints, it is possible to produce zygotes heterozygous for a deficiency for the region between the breakpoints, and also, as a complementary product, zygotes carrying a duplication for precisely the same region. A set of Y-autosome translocations with appropriately positioned breakpoints, therefore, can in principle be used to generate a non-overlapping set of deficiencies and duplications for the entire autosomal complement.-Using this method, we have succeeded in examining segmental aneuploids for 85% of chromosomes 2 and 3 in order to assess the effects of aneuploidy and to determine the number and location of dosage-sensitive loci in the Drosophila genome (Figure 5). Combining our data with previously reported results on the synthesis of Drosophila aneuploids (see Lindsley and Grell 1968), the following generalities emerge.-1. The X chromosome contains no triplo-lethal loci, few or no haplo-lethal loci, at least seven Minute loci, one hyperploid-sensitive locus, and one locus that is both triplo-abnormal and haplo-abnormal. 2. Chromosome 2 contains no triplo-lethal loci, few or no haplo-lethal loci, at least 17 Minute loci, and at least four other haplo-abnormal loci. 3. Chromosome 3 contains one triplo-lethal locus that is also haplo-lethal, few or no other haplo-lethal loci, at least 16 Minute loci, and at least six other haplo-abnormal loci. 4. Chromosome 4 contains no triplo-lethal loci, no haplo-lethal loci, one Minute locus, and no other haplo-abnormal loci.-Thus, the Drosophila genome contains 57 loci, aneuploidy for which leads to a recognizable effect on the organism: one of these is triplo-lethal and haplo-lethal, one is triplo-abnormal and haplo-abnormal, one is hyperploid-sensitive, ten are haplo-abnormal, 41 are Minutes, and three are either haplo-lethals or Minutes. Because of the paucity of aneuploid-lethal loci, it may be concluded that the deleterious effects of aneuploidy are mostly the consequence of the additive effects of genes that are slightly sensitive to abnormal dosage. Moreover, except for the single triplo-lethal locus, the effects of hyperploidy are much less pronounced than those of the corresponding hypoploidy.
584 citations
"Genetic analysis of a Minute mutati..." refers background in this paper
...Lindsley et al. (1972) showed that heterozygosity for small deletions spanning a great part of the D. 87...
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TL;DR: It is postulated that a chromomere is one cistron within which much of the DNA is regulatory in function.
Abstract: An average size chromomere of the polytene X chromosome of Drosophila melanogaster contains enough DNA in each haploid equivalent strand to code for 30 genes, each 1,000 nucleotides long. We have attempted to learn about the organization of chromosomes by asking how many functional units can be localized within a chromomere. This was done by 1) recovery of mutants representative of every cistron in the 3A2-3C2 region; 2) the characterization of the function of each mutant type and grouping by complementation tests; 3) the determination of the genetic and cytological position of each cistron by recombination and deletion mapping. The data clearly show one functional group per chromomere. It is postulated that a chromomere is one cistron within which much of the DNA is regulatory in function.
343 citations
"Genetic analysis of a Minute mutati..." refers background in this paper
...M(2)-ZB fine structure 93 Based on the number of cistron and amount of DNA in each chromomere, Judd et al. (1972) regarded each chromomere to consist mainly of regulatory element and the actual coding part (structural element) is very small....
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...A number of loci namely white (Judd et al., 1972), Notch (Welshons, 1965), rosy (Hillicker et al., 1980), alcohol dehydrogenase (Woodruff et al., 1979) and several others have been analysed in their detail by this technique, to understand more about their organizational complexity and fine…...
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TL;DR: The D. mlanogaster DNA used in the studies on ribosomal RNA permits the performance of the necessary experiments as well as others relevant to the following two questions: What proportion of the D. melanogaster genome is complementary to t- RNA?
Abstract: MOLECULAR hybridization (HALL and SPIEGELMAN 1961 ) of labeled ribosomal RNA (r-RNA) with DNA in D. mlanogaster has revealed (VERMEULEN and ATWOOD 1965; RITOSSA and SPIEGELMAN 1965) that, as in the bacteria (YANKOFSKY and SPIEGELMAN 1962a, b, 1963), approximately 0.27% of the DNA is complementary to r-RNA. This DNA is believed to constitute the ensemble of templates for the transcription of r-RNA and may be referred to as the r-DNA. The amount of r-DNA per haploid Drosophila genome is sufficient to complement at least 130 molecules each of 18s and 28s r-RNA. Inversions in the X chromosome of Drosophila melanoguster are available (SIDOROV 1930; STURTEVANT and BEADLE 1936; MULLER et al. 1937) from which one can derive X chromosomes possessing duplications or deletions of a heterochromatic region which includes the nucleolus organizer (NO). With these chromosomes, flies can be obtained which have from one to four doses of the NO region. With DNA from such flies, annealing experiments demonstrated ( RITOSSA and SPIEGELMAN 1965) that the amount of r-RNA hybridizable per unit of DNA was directly proportional to the dosage of the NO region per genome. These data indicated then that the DNA sequences complementary to the ribosomal RNA are confined to the segment contained in the deletion or duplication employed. The existence in bacteria of DNA complementary to amino acid transfer RNA (t-RNA) has been established ( GIACOMONI and SPIEGELMAN 1962; GOODMAN and RICH 1962). However, this issue has thus far not been taken up in the higher forms. It is, in principle, readily resolvable by molecular hybridization with suitably labeled and purified t-RNA. The D. melanogaster DNA used in the studies on ribosomal RNA permits the performance of the necessary experiments as well as others relevant to the following two questions: (1 ) What proportion of the D. melanogaster genome is complementary to t-RNA? (2) Are the DNA complements of t-RNA localized in the same region as those of the r-RNA? An answer to the first question is pertinent to possible interpretations of the 130-fold redundancy in ribosomal DNA complements. The second question is of obvious interest and gains particular importance from recent reports of t-RNA ' The In\\estigations reported here were supported by Grants GB-2169, GB-2700, GB-296 from the National Science Foundation, and by Public Health Service Research Grant No CA-01094 from the National Cancer Institute On leave from the International Laboratory of Genetics and Biophysics
134 citations
"Genetic analysis of a Minute mutati..." refers background in this paper
...Although no workable hypothesis has emerged, a number of propositions have been made to attribute an unitary function for all these loci (Brehme, 1939; Farnsworth, 1965; Ritossa et al., 1966; Sinclair et al., 1981)....
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124 citations
"Genetic analysis of a Minute mutati..." refers background in this paper
...A number of loci namely white (Judd et al., 1972), Notch (Welshons, 1965), rosy (Hillicker et al., 1980), alcohol dehydrogenase (Woodruff et al., 1979) and several others have been analysed in their detail by this technique, to understand more about their organizational complexity and fine structure....
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...A number of loci namely white (Judd et al., 1972), Notch (Welshons, 1965), rosy (Hillicker et al., 1980), alcohol dehydrogenase (Woodruff et al., 1979) and several others have been analysed in their detail by this technique, to understand more about their organizational complexity and fine…...
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TL;DR: The genetic analysis of a region of the third chromosome of Drosophila melanogaster extending from 87D2-4 to 87E12-F1, an interval of 23 or 24 polytene chromosome bands substantiate the conclusion drawn earlier that the rosy locus is the only gene in this region concerned with XDH activity and that all adjacent genetic units are functionally, as well as spatially, distinct from the roSy gene.
Abstract: This report describes the genetic analysis of a region of the third chromosome of Drosophila melanogaster extending from 87D2–4 to 87E12–F1, an interval of 23 or 24 polytene chromosome bands. This region includes the rosy (ry, 3–52.0) locus, carrying the structural information for xanthine dehydrogenase (XDH). We have, in recent years, focused attention on the genetic regulation of the rosy locus and, therefore, wished to ascertain in detail the immediate genetic environment of this locus. Specifically, we question if rosy is a solitary genetic unit or part of a larger complex genetic unit encompassing adjacent genes. Our data also provide opportunity to examine further the relationship between euchromatic gene distribution and polytene chromosome structure.——The results of our genetic dissection of the rosy microregion substantiate the conclusion drawn earlier (Schalet, Kernaghan and Chovnick 1964) that the rosy locus is the only gene in this region concerned with XDH activity and that all adjacent genetic units are functionally, as well as spatially, distinct from the rosy gene. Within the rosy micro-region, we observed a close correspondence between the number of complementation groups (21) and the number of polytene chromosome bands (23 or 24). Consideration of this latter observation in conjunction with those of similar studies of other chhromosomal regions supports the hypothesis that each polytene chromosome band corresponds to a single genetic unit.
100 citations