Labeled DNA Strands Research Articles

Arrangement and characterization of repetitive sequence elements in animal DNAs.

Recent investigations carried out in our laboratory have shown for several animal DNAs that repetitive and nonrepetitive sequences are interspersed in a generally ordered manner. The basic type of experiment on which this conclusion rests begins with the reassociation of trace quantities of long, labeled DNA fragments with short, unlabeled fragments present in excess. The mixture is incubated to low C0t, so that only repetitive sequences are reassociated, and is then passed over hydroxyapatite. Long, radioactive fragments which bind to the hydroxyapatite contain repetitive sequence elements paired with short, unlabeled DNA fragments. In the DNAs which have been studied in this manner, most of the bound labeled DNA strands include nonrepetitive sequences as well as the repetitive sequence elements causing the binding. Therefore, it is evident that the repetitive and nonrepetitive sequence elements must be closely interspersed in the genome. We...

Evidence for the attachment of RNA to pulse-labeled DNA in the slime mold, [formula omitted

When Physarum polycephalum is pulse-labeled for up to 20 minutes with 3H-thymidine and the shortest labeled DNA strands are partially purified by sedimentation through a neutral aqueous sucrose gradient and then through a formamide-sucrose gradient, these short strands band in Cs 2SO 4 isopycnic density gradients at a density greater than that of bulk single-stranded DNA. Their density is brought partially or nearly completely back to that of single-stranded DNA by hydrolysis with pancreatic RNase A or alkali, respectively. Therefore the dense material attached to the short pulse-labeled DNA strands consists at least partially of RNA.