RT Journal Article SR Electronic T1 DATABASE: Written in the Blood JF Science JO Science FD American Association for the Advancement of Science SP 1725 OP 1725 DO 10.1126/science.304.5678.1725e VO 304 IS 5678 YR 2004 UL http://science.sciencemag.org/content/304/5678/1725.5.abstract AB