We have recently reported that DNA and chromatin fragments derived from apoptotic cells that circulate in blood of human beings can readily enter into somatic cells of mice in vitro and in vivo, evoke a DNA damage repair response and integrate themselves into their genomes. However, these findings are at odds with established knowledge on two counts: first, DNA is not known to spontaneously enter into cells, and second, DNA is not known to have any intrinsic biological properties. We hypothesized that cellular entry and acquisition of biological properties are functions of the size of DNA. To test this hypothesis we isolated HMW DNA from cancerous and non-cancerous human cells, bacteria and plant and sonicated them to generate fragments similar in size to circulating DNA. Our early results show that while HMW DNAs are incapable of entering into mouse cells, sonicated DNA (sDNA) from human, bacteria and plant sources could do so spontaneously. Likewise, human, bacterial and plant sDNA could spontaneously enter into bacterial cells while their HMW counterparts could do so sparingly. The intracellular sDNA associated themselves with host cell chromosomes and integrated themselves into their genomes. We also demonstrate that sDNA, but not HMW DNA, from human, bacterial and plant sources can phosphorylate H2AX and activate the transcription factor NFkB in mouse cells, indicating that sDNAs have acquired biological properties. Taken together, our findings might provide a mechanistic explanation for reported evidence of horizontal transfer of genes in nature and suggest that extreme environmental stress leading to cellular apoptosis and DNA fragmentation may have played a significant role in adaptation and evolution of species.