 Studies found DNA from the M13 virus, Green fluorescent protein and RuBisCO genes in the blood and tissue of animals, and in 2012, a paper suggested that a specific microRNA from rice could be found at very low quantities in human and animal serum.Other studies however, found no or negligible transfer of plant microRNAs into the blood of humans or any of three model organisms.Another concern is that the antibiotic resistance gene commonly used as a genetic marker in transgenic crops could be transferred to harmful bacteria, creating resistant superbugs.