Adding to the atmosphere, a third member of their team has identified a part of the shroud's markings as that of blood from a human male. No one has conclusively determined how the markings got on the linen, but they appear in bas relief in a perfect negative image. Experts have entertained theories that the markings came from paint, scorching, or accelerated aging. Victor V. Tryon, PhD, assistant professor in microbiology and director of the university's Center for Advanced DNA Technologies, examined the DNA of one so-called "blood glob" from two separate microscopic shroud samples. He reported isolating signals from three different human genes by employing polymerase chain reaction, which can detect pieces of double-stranded DNA.