Isolation and some properties of a mammalian ribosomal DNA

Abstract

The DNA coding for 28 S and 18 S ribosomal RNA, including the spacer regions, has been isolated from calf (Bos taurus) thymus gland. The method used included shearing of the total DNA to a highly homogeneous size population, selective heat denaturation and S1 nuclease treatment to remove single stranded DNA. Repeated centrifugation on density gradients yields a 140-fold purified rDNA fraction with a GC content of 61.2% Eco RI nuclease cleaves this DNA into two fragments of 16.4 and 4.9 X 10(6) daltons. Hybridization of these fragments with 28 S and 18 S rRNA shows that the 28 S coding sequence is located mostly on the 4.9 X 10(6) dalton fragment, while both the 16.4 and 4.9 X 10(6) dalton fragments contain the 18 S sequence. The data indicate that the ribosomal RNA gene has a repeat unit of 21.3 X 10(6) daltons which includes a nontranscribed spacer of about 12.5 X 10(6) daltons.

An Analysis of the Bovine Genome by Density‐Gradient Centrifugation

“…Concerning the significance of minor components, so far, we have evidence from hybridization experiments that the 1.71 9-g/cm3 minor component contains ribosomal cistrons (M. Meunier, personal communication), in agreement with an independent report by other authors [8]. It is possible that other minor components may well correspond to other repetitive genes.…”

MMP‐8 ‐799 C>T genetic polymorphism is associated with the susceptibility to chronic and aggressive periodontitis in Taiwanese

“…Genomic DNA was extracted from peripheral leucocytes using standard phenol/chloroform extraction and precipitation with ethanol (Blin et al. ). The DNA concentration was determined by ultraviolet light spectrophotometry at 260 nm.…”

“…A 10-ml sample of peripheral blood was collected into EDTA coated vacutainer tubes by a standard venipuncture method from each subject. Genomic DNA was extracted from peripheral leucocytes using standard phenol/chloroform extraction and precipitation with ethanol (Blin et al 1976). The DNA concentration was determined by ultraviolet light spectrophotometry at 260 nm.…”

Structural characteristics of genome organization in amphibians: Differential staining of chromosomes and DNA structure

“…The number of rRNA genes also varies: in mice it is about 100 (Gaubatz et al 1975), in Rattus norvegicus -about 100-360 (Melli et al 1971), and in the cat -about 1000 (Szabo et al 1978). Although many details of rRNA gene organization in mammals remain unknown, it has been found that the size of repetitive units in them is about twice as great as it is in the case of amphibians (16.2-21.3x106 and 8x106 daltons respectively) (Southern 1975;Blin et al 1976;Arnheim and Southern 1977;Stambroock 1978;Meunier-Rotival et al 1979). As in amphibians, the absolute size of rDNA repeating units in mammals can also vary, due to variations in spacer length (Arnheim and Southern 1977;Stambroock 1978;Krystal and Arnheim 1978).…”