Partial denaturation mapping of cloned histone DNA from the sea urchin Psammechinus miliaris.

A cloned 5.6-kb DNA repeat unit of Psammechinus miliaris containing all five histone coding sequences of known order and polarity has been shown to fall clearly into a low melting and a high melting half by thermal denaturation. The topoligies of the DNA sequences thus defined were determined by partial denaturation mapping in the electron microscope to gain further insight into the distribution of spacers and genes within histone DNA.