Presence, isolation and characterization of yolk DNA from chicken eggs

Yolk DNA was detected with immunocytochemistry in fertilized chicken eggs. Yolk spheres were purified with Ficoll 400 density gradient centrifugation, followed by extraction of DNA therein. Yolk DNA is sensitive to various restriction endonucleases, but shows no obvious bands, demonstrating its sequence heterogeneity. There is only a little, if any, methylated CpG in yolk DNA, judging from MspI and HpaII digestion. Southern blot indicated that the sequence of yolk DNA accounts for a small portion of that of genomic DNA. Its uniqueness suggests that yolk DNA may play a crucial role in early development of chickens.