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Multiple Genomes

Rather than having one genome, people likely are made up of a number of different genomes, writes Carl Zimmer at the New York Times. This, he adds, may have medical implications.

“There have been whispers in the matrix about this for years, even decades, but only in a very hypothetical sense,” Alexander Urban, a geneticist at Stanford University, tells Zimmer. Urban adds that recent work has brought this idea out of the realm of the hypothetical.

Zimmer writes that not only do people contain DNA from their parents, they may also be chimeras and have contributions from a twin and, in the case of mothers, their children. Additionally, people may be mosaics and have tissues that developed from cells that acquired mutations early on during development and passed those changes on.

While most instances of chimerism or mosaicism appear to be benign, researchers are beginning to investigate their possible roles in diseases like schizophrenia.

A challenge, though, will be for genetic testing, Zimmer points out. If tests are run on a blood sample, that may not tell doctors and genetic counselors what variants there are, for example, in brain tissue.