Chimeras and Mosaics
No, I’m not talking about ancient mythology or art history.
These are two phenomena that can be found inside the average person’s DNA --
sometimes completely without his or her knowledge. In genetic research, a chimera
is a living thing with several populations of cells with different genetic
makeup originating from conception. Mosaic,
on the other hand, refers to “the presence of two populations of cells with
different genotypes in one individual who has developed from a single
fertilized egg.” A recent article
from the New York Times discussed the
possibility, probability and even instances of people with multiple, differing DNA
sequences co-existing in their bodies.
The article noted on the traditional presentation of our
genome. Originally, it was assumed that a person’s genome is the same regardless
of whether it comes from the blood, the heart, the liver or the brain, etc. New
research is examining the existence of multiple DNA strands within the same
person. Characteristics like mosaicism, which come from more spontaneous
mutations, were initially tracked as part of cancer clusters, but with the
wider accessibility of genetic sequencing, researchers are finding these traits
in more than just diseases.
“There have been whispers in the matrix about this for
years, even decades, but only in a very hypothetical sense,” commented
Alexander Urban, PhD, a geneticist at Stanford University, in the New York Times story.
According the New York
Times piece, early cases of patients with more than one genomic structure
began to emerge in the middle of the 20th century. The story noted a
woman in 1953, who donated blood that possessed qualities of both Types O and A
-- having “acquired some of her blood from her twin brother in the womb.”
Chimerism is also a common occurrence in women who have been pregnant and subsequently
taken on some of the genetic qualities of their children. The article went on,
noting studies in which Y chromosomes were detected in a surprising amount of
both breast and brain tissue.
As the technology to detect these characteristics becomes
more common, the cases in which they occur are being documented more
effectively. The New York Times discussed
the possibility of scenarios in which the presence of mosaicism and chimerism can
lead to both an increased susceptibility to diseases and disorders beyond being
at risk for cancer and as well as the potential benefits of these traits. Despite
more substantial research on the presence of multiple DNA strands in a single
person’s genome recently, the trait could complicate certain areas of the field
as it becomes more established.