Biomaterial Database

Transcripts from both strands of a satellite DNA occur on lampbrush chromosome loops of the newt Notophthalmus. 1981

M O Diaz, and G Barsacchi-Pilone, and K A Mahon, and J G Gall

We have isolated genomic DNA clones from the newt Notophthalmus which contain one or more copies of a 222 bp tandemly repeated sequence (satellite 1). Satellite 1 occurs in the pericentromeric heterochromatin of all chromosomes and at the sphere loci of chromosomes 2 and 6. Lampbrush chromosome loops associated with the spheres contain transcripts of satellite 1, as shown by in situ hybridization. The matrix on these loops consists of multiple thin--thick transcription units, most but not all of which have the same polarity within a given loop. By in situ hybridization with single-stranded probes we show that transcription units of opposite morphological polarity contain transcripts of opposite strands of satellite 1. Satellite 1 occurs as the spacer between clusters of histone genes. We postulate that transcription initiates at a histone gene promoter, fails to terminate at the end of the gene and continues without interruption into the adjacent satellite DNA. In this way, long transcripts are produced which contain both histone and satellite 1 sequences. A general failure of termination signals might explain the unusually long transcripts of lampbrush chromosomes.

UI	MeSH Term	Description	Entries
D008957	Models, Genetic	Theoretical representations that simulate the behavior or activity of genetic processes or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.	Genetic Models,Genetic Model,Model, Genetic
D009673	Notophthalmus viridescens	A species of newt in the Salamandridae family in which the larvae transform into terrestrial eft stage and later into an aquatic adult. They occur from Canada to southern United States. Viridescens refers to the greenish color often found in this species.	Diemictylus viridescens,Newt, Red-Spotted,Triturus viridescens,Newt, Red Spotted,Newts, Red-Spotted,Red-Spotted Newt,Red-Spotted Newts
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
D002875	Chromosomes	In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)	Chromosome
D003001	Cloning, Molecular	The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.	Molecular Cloning
D004276	DNA, Satellite	Highly repetitive DNA sequences found in HETEROCHROMATIN, mainly near centromeres. They are composed of simple sequences (very short) (see MINISATELLITE REPEATS) repeated in tandem many times to form large blocks of sequence. Additionally, following the accumulation of mutations, these blocks of repeats have been repeated in tandem themselves. The degree of repetition is on the order of 1000 to 10 million at each locus. Loci are few, usually one or two per chromosome. They were called satellites since in density gradients, they often sediment as distinct, satellite bands separate from the bulk of genomic DNA owing to a distinct BASE COMPOSITION.	Satellite DNA,Satellite I DNA,DNA, Satellite I,DNAs, Satellite,DNAs, Satellite I,I DNA, Satellite,I DNAs, Satellite,Satellite DNAs,Satellite I DNAs
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D012313	RNA	A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. (Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)	RNA, Non-Polyadenylated,Ribonucleic Acid,Gene Products, RNA,Non-Polyadenylated RNA,Acid, Ribonucleic,Non Polyadenylated RNA,RNA Gene Products,RNA, Non Polyadenylated
D014158	Transcription, Genetic	The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION.	Genetic Transcription
D015870	Gene Expression	The phenotypic manifestation of a gene or genes by the processes of GENETIC TRANSCRIPTION and GENETIC TRANSLATION.	Expression, Gene,Expressions, Gene,Gene Expressions