The Human Body is A Mosaic of A Single Cell, Not Genetic Clones

The human body has approximately 40 trillion cells that all progressed out of a single fertilized egg.  But this evolution, apparently, does not result in a perfect clones, at least not in terms of DNA. According to a new study the cells in our body are actually mosaic, meaning they have thousands of subtle genetic variations between them. 

Mutation is a normal, natural thing.  In fact, many species—and especially humans—rely on mutation for survival and differentiation.  Skin cells, for example, can turn into moles, but we can also find mutations along the esophagus and even in our blood. 

Of course, tumors begin as mutated cells…

Until recently, though, nobody has tried to characterize these cells across the many different types of tissue in the human body, measuring them against a wide variety and great number of individual specimens.  Thus, MIT Broad Institute postdoctoral researcher Keren Yizhak led a study that analyzed the genetic information throughout 29 different tissues taken from approximately 500 people.  Sure enough, the found mutant cell populations in almost every person involved. 

Yizhak comments, “The skin, the lung, and the esophagus were the ones where we found the highest amount of mutations.”

This makes sense, of course, because these tissues are always renewing and restructuring themselves. They are in constant repair, essentially, after consistent bombardment from the sun and other things that can potentially damage the skin (like smoke in the lungs, for example). 

Scientists also found mutations in diseased tissue—like tumors—but that, of course, is totally normal (and different from the new discovery). Furthermore, these mutations are perfectly normal, asserts Gad Getz, who runs the lab where Yizhak conducted the study.  The thing is, these mutations are not cancerous, Getz says.

Specifically, Getz notes that we are all unique puzzles with different pieces of different sizes.  Every piece is similar to the original DNA but it is more likely that we are “actually a mosaic of cells with small variations” than millions (or more) clones of the same cell. 

Scientists say that while this discovery is novel, it might have more important implications in terms of things like detecting cancer.  As it turns out, many of these mutations that cause overpopulation of cells can, in fact, be involved with cancer growth. That in mind, cancer tests could be fooled by these mutations; so this could lead to better diagnosis tools in the future. 

The study has been published in the journal Science.