[ExI] DNA Double Take

BillK pharos at gmail.com
Fri Sep 20 20:05:28 UTC 2013

Scientists are discovering that — to a surprising degree — we contain
genetic multitudes. Not long ago, researchers had thought it was rare
for the cells in a single healthy person to differ genetically in a
significant way. But scientists are finding that it’s quite common for
an individual to have multiple genomes.


Chimerism, as such conditions came to be known, seemed for many years
to be a rarity. But “it can be commoner than we realized,” said Dr.
Linda Randolph, a pediatrician at Children’s Hospital in Los Angeles
who is an author of a review of chimerism published in The American
Journal of Medical Genetics in July.

Last year, for example, forensic scientists at the Washington State
Patrol Crime Laboratory Division described how a saliva sample and a
sperm sample from the same suspect in a sexual assault case didn’t

Bone marrow transplants can also confound forensic scientists.
Researchers at Innsbruck Medical University in Austria took cheek
swabs from 77 people who had received transplants up to nine years
earlier. In 74 percent of the samples, they found a mix of genomes —
both their own and those from the marrow donors, the scientists
reported this year. The transplanted stem cells hadn’t just replaced
blood cells, but had also become cells lining the cheek.


So, if people can be mixtures of DNA, how do we know which DNA is the
hereditary one?
And, if different organs can have different DNA, what does that say
about susceptibility to disease?


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