Staining of satellite DNA in metaphase chromosomes.

Abstract

A SIMPLE technique is described here which locates regions of satellite or highly repetitive DNA within mammalian metaphase chromosomes and helps the study of relationships between these regions and those which are heterochromatic and late replicating. The technique arose from attempts to hybridize radioactively labelled satellite DNA from mouse1, guineapig2 and calf3 in situ with complementary regions in metaphase chromosomes, as described by Jones4 and Pardue and Gall5. The areas of hybrids formed in this manner were always located around the centromere. Using the Giemsa stain we also observed that these areas stained more darkly than the remainder of the chromosome material on denaturation and reassociation in situ, without the addition of satellite DNA. This indicated that, even in these conditions, there is re-association of the satellite DNA strands and that there may be a simpler technique in which no satellite DNA need be added. Ideally, a clear picture of the satellite DNA would be obtained in metaphase chromosomes by denaturing the DNA strands and allowing them to reassociate for varying times in an adequate buffer. In this manner, with increasing time of reassociation there would be within the chromosomes a progression of darkly staining regions of satellite DNA which would contrast sharply with lightly staining regions of the remaining DNA.