Heat and alkali induced hyperchromic effects in the ribosomal DNA of sea urchin (Lytechinus variegatus) sperm.

Melting point dispersion analysis of the ribosomal DNA (rDNA) of sea urchin (Lytechinus variegatus) sperm shows a scatter in the Tm obtained at wavelengths of 230-280 nm at 5 nm intervals. The dispersion curve of the rDNA, which lies in between human thymus DNA and T2 DNA, is probably suggestive of the intragenic heterogeneity. Alkali induced hyperchromic effects, examined over 220-290 nm at 5 nm intervals, show that the hyperchromic effect is minimum at 250 nm, followed by a sharp increase around 270-275 nm. These findings are consistent with the hyperchromic effects produced by alkali-melted G + C--rich DNA of lower organisms.