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Title:Localization of Small-Nuclear-Rna Genes of Drosophila Melanogaster on Polytene Chromosomes
Author(s):Nag, Abhijit
Department / Program:Genetics and Development
Discipline:Genetics and Development
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Biology, Genetics
Abstract:The existence of discrete, stable, small nuclear RNAs (snRNAs) is known since 1960s. These RNAs range in size from 90-300 nucleotides and are confined to eukaryotic nuclei. snRNAs have been well-characterized biochemically and have been isolated and sequenced from different organisms. Recent observations that these RNAs associate with hnRNA and small nuclear ribonucleoproteins (snRNPs) act as antigens that are precipitated by antibodies from patients with lupus erythematosus, an auto-immune rheumatic disease, have sparked new interest in these molecules. snRNAs have been found to be highly conserved in evolution and certain regions of these RNAs show complementarity to intron/exon splice junctions. This has led to the suggestion that snRNAs act as mediators in mRNA processing. However, there is no direct evidence.
In this project Drosophila snRNAs, larger than 5S RNA, were isolated and mapped on polytene chromosomes. A rough estimate of the size of snRNAs shows them to have between 100-275 nucleotides. From hybridization kinetics their gene copy number seems to be 100-400. Mapping of snRNA genes shown certain interesting features. First, they map on developmental puffs. All snRNA puff sites are not active throughout, however, at least two sites are active at any given time. Second, snRNAs are localized on doublets or two adjacent bands, indicating that they are repeated. Finally snRNAs tend to cluster. Three snRNAs map on chromosome 2(L) - snDm 2 at 29DE, snDm 3 at 28C and snDm 6 at 29EF, 30A; three map on chromosome 3(R) - snDm 4, 5 and 7 at 95BC, 83D and 95EF respectively and only one maps by itself on 3(L) - snDm 5 at 65CD.
Issue Date:1981
Description:58 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1981.
Other Identifier(s):(UMI)AAI8203539
Date Available in IDEALS:2015-05-14
Date Deposited:1981

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