Feb 15, 2024 09:20 PM
https://www.discovermagazine.com/the-sci...ets-of-dna
EXCERPTS: Most of us are the product of a single genetic code. When our parents conceive us, their chromosomes combine to form the unique sequence of DNA that we carry with us for the rest of our lives. Under the right circumstances, however, it's possible for one body to contain two distinct genomes.
[...] One recipe for chimerism begins during pregnancy with twins (or triplets, octuplets, etc.). In cases of vanishing twin syndrome, where one of the embryos dies in utero, the other may absorb its cells and become a being divided — it will still have its original genes, but they’ll be mixed with those of its less fortunate womb-mate. (Of course, this only works with fraternal twins, since identical twins already share the exact same DNA.)
That’s what happened to Lydia Fairchild, a woman who almost lost custody of her children in 2002 after DNA testing showed she wasn’t a genetic match with them. Luckily a second test, this time on cells from a different part of her body, set the record straight: Fairchild was a hybrid, partly herself and partly a twin sister she’d carried with her all her life. So, she was indeed her children’s mother — but also, genetically speaking, she was their aunt.
[...] These twin scenarios may sound extraordinary, but there are even more routine ways to gain a second set of DNA. When a woman is pregnant with just one child, either (or both) of them may become chimeric if their respective cells cross the placental barrier that separates mother and fetus. These stowaways can enter the other’s bloodstream, travel to distant organs, and establish themselves alongside native cells.
In 2012, for example, a team of medical researchers from Washington state performed autopsies on the brains of 59 women. Astonishingly, 37 of them — nearly two thirds — harbored cells with Y chromosomes, which are only present in males. Clearly, they weren’t homegrown...
[...] Everything thus far falls under the category of “natural” chimeras, people who come by their dual DNA in the course of normal human development. But, later in life, a person can also become an “artificial” chimera. All it takes is a quick medical operation. ... When a person receives a donated organ (say, a kidney), the tissue retains its old genes. The same is true for bone marrow — when someone’s diseased marrow is swapped out for a healthy substitute, the new blood cells it produces have the donor’s DNA... (MORE - missing details)
EXCERPTS: Most of us are the product of a single genetic code. When our parents conceive us, their chromosomes combine to form the unique sequence of DNA that we carry with us for the rest of our lives. Under the right circumstances, however, it's possible for one body to contain two distinct genomes.
[...] One recipe for chimerism begins during pregnancy with twins (or triplets, octuplets, etc.). In cases of vanishing twin syndrome, where one of the embryos dies in utero, the other may absorb its cells and become a being divided — it will still have its original genes, but they’ll be mixed with those of its less fortunate womb-mate. (Of course, this only works with fraternal twins, since identical twins already share the exact same DNA.)
That’s what happened to Lydia Fairchild, a woman who almost lost custody of her children in 2002 after DNA testing showed she wasn’t a genetic match with them. Luckily a second test, this time on cells from a different part of her body, set the record straight: Fairchild was a hybrid, partly herself and partly a twin sister she’d carried with her all her life. So, she was indeed her children’s mother — but also, genetically speaking, she was their aunt.
[...] These twin scenarios may sound extraordinary, but there are even more routine ways to gain a second set of DNA. When a woman is pregnant with just one child, either (or both) of them may become chimeric if their respective cells cross the placental barrier that separates mother and fetus. These stowaways can enter the other’s bloodstream, travel to distant organs, and establish themselves alongside native cells.
In 2012, for example, a team of medical researchers from Washington state performed autopsies on the brains of 59 women. Astonishingly, 37 of them — nearly two thirds — harbored cells with Y chromosomes, which are only present in males. Clearly, they weren’t homegrown...
[...] Everything thus far falls under the category of “natural” chimeras, people who come by their dual DNA in the course of normal human development. But, later in life, a person can also become an “artificial” chimera. All it takes is a quick medical operation. ... When a person receives a donated organ (say, a kidney), the tissue retains its old genes. The same is true for bone marrow — when someone’s diseased marrow is swapped out for a healthy substitute, the new blood cells it produces have the donor’s DNA... (MORE - missing details)
