Genes: The Older (Not) the Better

As we know, genes are linked to disease. In The Economist this week, there’s an article about how old genes cause more disease than young ones. “Old” in this case means historically old.

Using an approach called phylostratigraphy, Tomislav Domazet-Loso and Diethard Tautz of the Max-Planck Institute for Evolutionary Biology in Plön, Germany, compared genomes of species from different parts of the tree of life to figure out when a particular gene first appeared:

Something shared by multicellular animals but not found in protozoa, for example, probably arose about 700m years ago, when multicellularity appeared. Something found in amphibians, reptiles, birds and mammals, but not fish, would be about 370m years old—the point in history when limbs evolved. Using this information, the two researchers were able to trace the ages of genes implicated in genetic disease.

In a paper published in Molecular Biology and Evolution, the researchers explain that “the majority of disease-causing genes were present in single-celled organisms and that most of the rest arose when multicellular creatures began to evolve. Genes specific to mammals, by contrast, barely ever carry diseases.”

The next step in the team’s research is to develop an explanation for why genetic diseases “seem to be caused so disproportionately by old genes.” Genes, that apparently, are crucial to our existence: “The older a gene is, the more likely it is to be part of the irreducible structure of being alive, and therefore the more likely it is that breaking that gene will be fatal.”

Image credit: DNA stub from Wikipedia

Laura Moorhead