Repeated Sequences in DNA

“Cytoplasmic” DNA from primary embryonic cell cultures is not informational

“…It is possible to compare the sequence heterogeneity of nuclear and "cytoPlasmic" DNA by comparing the rates of reannealing after melting under similar conditions. Tiffs has been done for both the intermediate and slow annealing fractions [12,13] of the DNA, and the nuclear and "cytoplasmic" DNAs from primary cultures of embryonic mouse liver cells have very similar reannealing profiles. It can thus be concluded that the nuclear and "cytoplasmic" DNAs are similar in their sequence heterogeneity as in all other properties investigated.…”

Effects of cortisol on RNA synthesis as detected by hybridization with differentially renaturing DNA species

“…These experiments cannot differentiate between DNA species with respect to reassociation kinetics. Britten and Davidson [4] using the hydroxyapatite method of Bernardi [9] were able to resolve sheared DNA into different species, some of which renature very rapidly (repetitive sequences) whereas others show a very slow renaturation kinetic (unique fraction). It was therefore of interest to examine the hybridization capacity of newly formed RNA induced by different simuli with these different DNA species.…”

“…On the basis of hybridization-competition experiments, Drews and Brawerman [3] proved that cortisol causes the appearance of new species of RNA in rat liver nuclei. Recent studies of Britten and Kohne [4] on the reassociation kinetics of DNA gave evidence that DNA of higher organisms is composed of different types of sequences with respect to their renaturation kinetics. From these experiments, they postulated the existence of "highly repetitive" and "unique" sequences.…”

The occurrence of circular structures in highly reiterated DNA of the rat

“…Under the same experimental conditions no circular forms of phage T, , Escherichiu coli, and Bacillus subtilis DNA are observed. Thus, besides kinetic measurements of renaturation rate [6], the ability of DNA to form the circles seems to be the most adequate way to reveal reiterated DNA sequences as pointed out by Thomas et al [l] . On the other hand, one may expect that molecules which are involved in cyclization processes are physically in equilibrium with linear molecules and with higher linear aggregates (concatemers) derived from the latter.…”

“…Then the mixture was deproteinized by chloroform-isoamyl alcohol (24: 1, v/v). DNA was sheared mechanically as previously described [4] down to about 6-10 S *,,,w. Approximate sedimentation coefficients were calculated from band sedimentation in 5-20% sucrose gradient as described [5], Sheared DNA was fractionated according to Britten and Kohne [6] (for details see also [4] ), and arbitrary fractions renaturing at three kinetic rates have been obtained: fast, intermediate and slow [2,7]. The fast fraction has been obtained at C, t -10e3 mole set 1-l .…”