Related satellite DNA's in the genus Mus

Abstract

Several Thailand species from the genus Mus have been shown to contain satellite DNA's able to cross-reassociate with the Mus musculus satellite. One species, Mus caroli, contains at least three discrete but related light satellite DNA's. All the related Mus satellites band on the light side of the major band in neutral CsCl gradients, separate into complementary strands in alkaline CsCl gradients, and have a relatively low affinity for Ag +. Three of the Mus satellite DNA's have been purified: taken separately, they show very sharp thermal transitions and reassociate at similar rates to give well-matched duplexes. Separated, 32P-labelled strands of M. musculus satellite DNA cross-reassociate rapidly with the purified Thailand mice satellites. Very poorly-matched hybrid duplexes are formed, yet these melt off hydroxylapatite columns over a narrow temperature range. It is concluded that the related Mus satellite DNA's were produced by independent events of massive replication involving a single unstable sequence element inherited from a common ancestor species. The evidence from intersatellite reassociation and from pyrimidine tract analysis of the M. musctdus satellite suggests that the unstable satellite ancestor was itself a diverged repeating sequence, with a basic complexity of only 8 to 20 nucleotide pairs.