[Properties of satellite DNA from Brassica nigra].

The DNA components of B. nigra were preparatively separated by equilibrium ultracentrifugation in a CsCl density gradient, the buoyant density of the main component being 1,696 g . cm-3, that of the satellite component--1,704 g . cm-3. The properties of individual DNA fractions were investigated. Four major components could be observed on the differential melting curve of satellite DNA. Using the reassociation kinetics method it was shown that 30% of satellite DNA are presented as a fast reassociating component with a length of a repeated unit of approximately 2,5 . 10(3) nucleotide pairs. The calculated values of Tm and buoyant density suggest that the m5C content in satellite DNA is lower than that in the main component. During equilibrium ultracentrifugation in the density gradients of actinomycin D--CsCl and Hg2+--Cs2SO4 the satellite DNA is split into 4 major components.