ABO blood group system
The human reference genome is derived from thirteen anonymous volunteers from Buffalo, New York. Donors were recruited by advertisement in "The Buffalo News", on Sunday, March 23, 1997. The first ten male and ten female volunteers were invited to make an appointment with the project's genetic counselors and donate blood from which DNA was extracted. As a result of how the DNA samples were processed, about 80 percent of the reference genome came from eight people and one male, designated RP11, accounts for 66 percent of the total. The ABO blood group system differs among humans, but the human reference genome contains only an O allele, although the others are annotated).