The Chromosome Distribution of Homologous Sequences to the Four Human Satellite DNAs in the Hominidae

Abstract

Techniques of in situ hybridisation, developed by Gall and Pardue (1969), have enabled us to detect and localize repetitive DNA sequences in chromosomes. This method has frequently been applied to study the chromosome distribution of repetitive DNA sequences in man. Each human satellite DNA has been used as a template for in vitro synthesis of a radioactively complementary RNA (cRNA), using a bacterial DNA-dependent RNA polymerase. Each cRNA was then applied to denatured human chromosome preparations, and the sites where stable cRNA-DNA hybrids were formed were subsequently identified with autoradiography. Different amounts of these hybrid molecules, both in vitro and in situ, may be formed according to the temperature of incubation (Moar et al., 1975), because each of the three human satellite DNAs (I, II, and III) proved to have an optimum temperature (T OPT) at which cRNA-DNA hybridisation was most effective. Above their respective T OPJ, the amount of hybridisation detected in vitro and in situ decreased.