Biomaterial Database

Ribosomal DNA magnification in Saccharomyces cerevisiae. 1978

D B Kaback, and H O Halvorson

Strains monosomic for chromosome I of Saccharomyces cerevisiae contain 25 to 35% fewer rRNA genes than do normal diploid strains. When these strains are repeatedly subcultured, colonies are isolated that have magnified their number of rRNA genes to the diploid amount while remaining monosomic for chromosome I. We have determined the amount of DNA complementary to rRNA in viable haploid spores derived from a magnified monosomic strain. Some of these haploids contained 24 to 48% more rRNA genes than a normal euploid strain. These extra genes may be responsible for the increased number of rRNA genes in the strain monosomic for chromosome I. Genetic analysis of the haploids containing extra rRNA genes suggested that these genes are linked to chromosomal DNA and are heterozygous. They were not closely linked to any centromere and were not located on chromosome I. Furthermore, all the DNA complementary to rRNA in one of these haploid strains with magnified rRNA genes sedimented at a chromosomal molecular weight, consistent with chromosomal linkage. In addition, several new mutations mapping on chromosome I were used to show that ribosomal DNA magnification was not due to a chromosome I duplication.

UI	MeSH Term	Description	Entries
D008540	Meiosis	A type of CELL NUCLEUS division, occurring during maturation of the GERM CELLS. Two successive cell nucleus divisions following a single chromosome duplication (S PHASE) result in daughter cells with half the number of CHROMOSOMES as the parent cells.	M Phase, Meiotic,Meiotic M Phase,M Phases, Meiotic,Meioses,Meiotic M Phases,Phase, Meiotic M,Phases, Meiotic M
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
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
D004261	DNA Replication	The process by which a DNA molecule is duplicated.	Autonomous Replication,Replication, Autonomous,Autonomous Replications,DNA Replications,Replication, DNA,Replications, Autonomous,Replications, DNA
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
D012441	Saccharomyces cerevisiae	A species of the genus SACCHAROMYCES, family Saccharomycetaceae, order Saccharomycetales, known as "baker's" or "brewer's" yeast. The dried form is used as a dietary supplement.	Baker's Yeast,Brewer's Yeast,Candida robusta,S. cerevisiae,Saccharomyces capensis,Saccharomyces italicus,Saccharomyces oviformis,Saccharomyces uvarum var. melibiosus,Yeast, Baker's,Yeast, Brewer's,Baker Yeast,S cerevisiae,Baker's Yeasts,Yeast, Baker
D013172	Spores, Fungal	Reproductive bodies produced by fungi.	Conidia,Fungal Spores,Conidium,Fungal Spore,Spore, Fungal
D014178	Translocation, Genetic	A type of chromosome aberration characterized by CHROMOSOME BREAKAGE and transfer of the broken-off portion to another location, often to a different chromosome.	Chromosomal Translocation,Translocation, Chromosomal,Chromosomal Translocations,Genetic Translocation,Genetic Translocations,Translocations, Chromosomal,Translocations, Genetic