Inspired by a recently published article in the ZEIT (in German only), I did some further reads on the topic of mosaicism. The bottom line: contrary to common belief and what is taught in text books (and University courses), the human body does not consist of cells with a single, personal genome, but instead each cell or cell-cluster has it’s own personal genome. A phenomenon that is also called “mosaicism”.

Until recently we needed a bunch of cells that were used to sequence our DNA, but today we are able to look on our genes on a single-cell basis. Findings now reveal a new theory on how our cells and tissue has evolved and allows for new theories on somatic and psychiatric illnesses.

From a review by Biesecker and Spinner (2013)¹:

It has long been known that cancer is a mosaic genetic disorder, but mosaicism is now apparent in a diverse range of other clinical disorders, as indicated by their tissue distributions and inheritance patterns. Recent technical advances have uncovered the causative mosaic variant underlying many of these conditions and have provided insight into the pervasiveness of mosaicism in normal individuals.

This not only changes how we should think about the genetic basis of diseases but also about the genetic basis for personality and “normal” human behavior.

From this findings new theories of genetics and the genetic causes of human differences and diseases will emerge. We are not a single piece of cells with a pre-determined DNA, but a bunch of cells with different and still ongoing mutations in a DNA, that begun with only a single cell. This is fascinating and shows the ever-evolving nature of science and that we have by no means already “discovered everything that can be discovered”.

Further reads

• Zimmer, C. (2013). “The Dark Matter of Psychiatric Genetics”, Phenomena, A Science Salon (National Geographic). http://phenomena.nationalgeographic.com/2013/12/20/the-dark-matter-of-psychiatric-genetics/
• Lupski, J. R. (2013). Genome Mosaicism–One Human, Multiple Genomes. Science, 341(6144), 358–359. http://doi.org/10.1126/science.1239503