| Abstract: | Embryonic chick DNA from different tissues was examined for differences which might indicate specific DNA amplification in somatic cells. The problem was approached by determining the DNA compositional heterogeneity and searching for possible variation in different tissues of the 12-day chick. Neural retina, muscle, and whole decapitated (general) chick DNA were analyzed in CsCl and Cs2SO4 density gradients. While overloaded CsCl gradients showed a main band (rho = 1.701 g/cm3) and a heavy shoulder (rho = 1.716 g/cm3), overloaded Cs2SO4 gradients displayed a main band (rho = 1.426 g/cm3) and a discrete heavy satellite (rho = 1.447 g/cm3). This satellite, comprising approximately 1% of the whole cell DNA, appeared to be of nuclear origin and not related to mitochondrial DNA, which was found to have a density of 1.426 g/cm3 in Cs2SO4. No differences were found in the densities of the main band or the satellite DNA in the DNA samples isolated from the different tissues. However, the method of DNA isolation was found to be of crucial importance when comparing satellite DNA's among different tissues. |
