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Science Frontiers ONLINE No. 105: May-Jun 1996 |
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Mixed-up people
Mother-child chimeras. Investigators have discovered cells carrying male DNA among a mother's blood cells 27 years after the birth a male child. Evidently, descendents of fetal cells escape during pregnancy and persist in the mother for years after birth. The mother thus becomes a blend of herself and her child (or, possibly, children) - a kind of chimera.
The question is: Why doesn't the mother's immune system destroy these foreign cells? Some scientists speculate that these escaped and still-surviving cells may help explain why women are more susceptible than men to autoimmune diseases.
(Travis, J.; "Kids: Getting under Mom's Skin for Decades," Science News, 149:85, 1996)
Fatherless blood. In Britain, a male child has been found with normal skin, with each cell carrying the expected X and Y chromosomes, but "his" blood is all female. Its cells contain the mother's two X chromosomes with no paternal contribution. What happened? One theory is that the mother's unfertilized egg spontaneously divided. Then, fertilization occurred, but it was only partial. The sperm got to just one of the two or more cells derived from the egg. The embryo continued to develop but it was part all-mother and part mother-father! "Partial parthenogenesis" seems to be the proper term here.
The affected "boy" also has noticeably asymmetrical facial features. Since one in every few hundred people display slight facial asymmetry, partial parthenogenesis may be more common than usually thought.
(Cohen, Philip; "The Boy Whose Blood Has No Father," New Scientist, p. 16, October 7, 1995)