The incident involved a 34-year-old man from Washington State. He and his partner welcomed a son in 2014 via a fertility clinic. After realizing the baby’s blood type did not match either parent, the father took a standard paternity test. The results claimed he shared only 10% of his DNA with the child, declaring he was not the biological father.
Fearing a catastrophic error or mix-up at the fertility clinic, the couple hired a lawyer and consulted geneticist Barry Starr at Stanford University.
- Vanishing Twin Syndrome: Early in his mother’s pregnancy, the father was a fraternal twin. The other twin died early in the womb and was reabsorbed by the surviving embryo.
- Two Sets of DNA: Instead of disappearing completely, the cells of the deceased twin fused with the father. He became a human chimera—a person possessing two entirely distinct sets of DNA.
- The Ghost Genome: The father’s saliva and cheek cells carried his own DNA, but his reproductive organs carried his unborn brother’s DNA. The sperm cell that fertilized the mother’s egg belonged genetically to the twin who was never born.
This was the first documented case in medical history where a paternity test was fooled by human chimerism. (A similar maternal case occurred in 2002 to a Washington woman named Lydia Fairchild, whose children initially showed no genetic match to her).
- Two separate eggs are fertilized by two separate sperm cells at the same time.
- This process normally creates fraternal twins.
- In a chimera case, the two separate fertilized eggs fuse together very early in development.
- The resulting single embryo grows normally but contains two completely different sets of DNA.
- Some organs in the body develop from the first set of DNA, while other organs develop from the second set.
