Biomaterial Database

Sequence arrangement of the rDNA of Drosophila melanogaster. 1977

M Pellegrini, and J Manning, and N Davidson

The sequence arrangement of genes coding for stable rRNA species and of the interspersed spacers on long single strands of rDNA purified from total chromosomal DNA of Drosophila melanogaster has been determined by a study of the structure of rRNA:DNA hybrids which were mounted for electron microscope observation by the gene 32-ethidium bromide technique. One repeat unit contains the following sequences in the order given. First, an 18 S gene of length 2.13 +/- 0.17 kb. Second, an internal transcribed spacer (Spl) of length 1.58 +/- 0.15 kb. A short sequence coding for the 5.8S and perhaps the 2S rRNA species is located within this spacer. Third, the 28S gene with a length of 4.36 +/- 0.23 kb. About 55% of the 28S genes are unbroken or continuous (C genes). However, about 45% of the 28S genes contain an insertion of an additional segment of DNA that is not complementary to rRNA (l genes). The insertion occurs at a reproducible point 2.99 +/- 0.26 kb from the junction with Spl. The insertions are heterogeneous in length and occur in three broad size classes: 1.42 +/- 0.47, 3.97 +/- 0.55, and 6.59 +/- 0.62 kb. Fourth, an external spacer between the 28S gene and the next 18S gene which is presumably mainly nontranscribed and which has a heterogeneous length distribution with a mean length and standard deviation of 5.67 +/- 1.92 kb. Short inverted repeat stems (100-400 nucleotide pairs) occur at the base of the insertion. It is known from other studies that I genes occur only on the X chromosome. The present study shows that the I and C genes on the X chromosomes are approximately randomly assorted. The sequence arrangement on the plasmid pDm103 containing one repeat of rDNA (Glover et al., 1975) has been determined by similar methods. The I gene on this plasmid contains an inverted repeat stem. The occurrence of inverted repeat sequences flanking the insertion supports the speculation that these sequences are translocatable elements similar to procaryotic translocons.

UI	MeSH Term	Description	Entries
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D009690	Nucleic Acid Conformation	The spatial arrangement of the atoms of a nucleic acid or polynucleotide that results in its characteristic 3-dimensional shape.	DNA Conformation,RNA Conformation,Conformation, DNA,Conformation, Nucleic Acid,Conformation, RNA,Conformations, DNA,Conformations, Nucleic Acid,Conformations, RNA,DNA Conformations,Nucleic Acid Conformations,RNA Conformations
D009693	Nucleic Acid Hybridization	Widely used technique which exploits the ability of complementary sequences in single-stranded DNAs or RNAs to pair with each other to form a double helix. Hybridization can take place between two complimentary DNA sequences, between a single-stranded DNA and a complementary RNA, or between two RNA sequences. The technique is used to detect and isolate specific sequences, measure homology, or define other characteristics of one or both strands. (Kendrew, Encyclopedia of Molecular Biology, 1994, p503)	Genomic Hybridization,Acid Hybridization, Nucleic,Acid Hybridizations, Nucleic,Genomic Hybridizations,Hybridization, Genomic,Hybridization, Nucleic Acid,Hybridizations, Genomic,Hybridizations, Nucleic Acid,Nucleic Acid Hybridizations
D010957	Plasmids	Extrachromosomal, usually CIRCULAR DNA molecules that are self-replicating and transferable from one organism to another. They are found in a variety of bacterial, archaeal, fungal, algal, and plant species. They are used in GENETIC ENGINEERING as CLONING VECTORS.	Episomes,Episome,Plasmid
D004247	DNA	A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).	DNA, Double-Stranded,Deoxyribonucleic Acid,ds-DNA,DNA, Double Stranded,Double-Stranded DNA,ds DNA
D004331	Drosophila melanogaster	A species of fruit fly frequently used in genetics because of the large size of its chromosomes.	D. melanogaster,Drosophila melanogasters,melanogaster, Drosophila
D005796	Genes	A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms.	Cistron,Gene,Genetic Materials,Cistrons,Genetic Material,Material, Genetic,Materials, Genetic
D012335	RNA, Ribosomal	The most abundant form of RNA. Together with proteins, it forms the ribosomes, playing a structural role and also a role in ribosomal binding of mRNA and tRNAs. Individual chains are conventionally designated by their sedimentation coefficients. In eukaryotes, four large chains exist, synthesized in the nucleolus and constituting about 50% of the ribosome. (Dorland, 28th ed)	Ribosomal RNA,15S RNA,RNA, 15S
D012730	Sex Chromosomes	The homologous chromosomes that are dissimilar in the heterogametic sex. There are the X CHROMOSOME, the Y CHROMOSOME, and the W, Z chromosomes (in animals in which the female is the heterogametic sex (the silkworm moth Bombyx mori, for example)). In such cases the W chromosome is the female-determining and the male is ZZ. (From King & Stansfield, A Dictionary of Genetics, 4th ed)	Gonosomes,Chromosome, Sex,Chromosomes, Sex,Gonosome,Sex Chromosome