National Geographic

Where Genes Come From

In today’s New York Times, I’ve written a story about a simple but important question: where do new genes come from?

Some four billion years ago, when cellular life emerged, a typical primordial microbe likely had only a small set of genes. Today, however, genes abound. We, for example, have 20,000 genes that encode proteins. Dogs have their own set, and so do starfish and fireflies and willow trees and every other species on Earth.

Somehow, in all that time, evolution produced a lot of new genes. As I explain in my story, one way to make a new gene is to copy an old one. The two duplicates can then evolve in different directions. Duplicate each of them, and now one gene has become four. There’s plenty of evidence that gene duplication drives the origin of a lot of new genes.

But there are other ways. In my story, I focus on one example. In animals and plants and related species (known collectively as eukaryotes), protein-coding genes are nestled in vast stretches of DNA that don’t code for proteins. It takes only a modest mutation to non-coding DNA to get a cell to read some non-coding DNA and treat it like a gene. The protein the cell makes may be a complete mess, or it may be harmless. As I write in my story, there’s a growing body of evidence that this process generates new protein-coding genes at a steady clip. In fact, so many new genes have arisen that scientists are trying to figure out why species don’t have many more genes than they do. (The answer seems to be that sometimes the new genes get accidentally deleted as DNA gets copied.)

I didn’t have the space to discuss the other ways new genes evolve. Sometimes mutations will change the point where a cell starts to read a gene, for example, shifting down the length of DNA. The result may be a new protein with a new structure. A microbe may pass a gene to another species, and the gene in each species may then evolve in different directions.

What’s fascinating to me about the evolution of new genes is that it changes the way I think of evolution as a whole. I sometimes think of the genes in an organism as the musicians in an orchestra. As each gene evolves, I imagine each musician playing a new melody. But evolution can invite new musicians to pull up a chair and add their music to the song.

 

There are 5 Comments. Add Yours.

  1. Wayne
    May 1, 2014

    David Begun has also recently found female-specific orphan genes in Drosophila:

    http://abstracts.genetics-gsa.org/cgi-bin/dros14s/showdetail.pl?absno=14531505

  2. Basil Hall
    May 3, 2014

    Has no one considered that evolution, at least on Earth, was a matter of switching off and loosing genes that already existed in what I have called the Primal Egg. This would mean that evolution was a defuse “emryology” of LIFE, each stage laying down the conditions that would allow and kick start the next phase of change.

    This would explain the Cambrian explosion and the fact that, in the case of humans, different hominins evolving with various combinations of human/ape characteristics.

    I believe that, in general, evolution at the phylum level was already programmed in to the primal egg and Darwinian evolution was a response to the different conditions LIFE might encounter on different planets or when the conditions on a single planet changed rapidly on a geological level.

    I have put my ideas into an illustrated poem, you can find at:

    https://sites.google.com/site/basilhughhall/p-e

  3. Richard M Williams Jr.
    May 5, 2014

    how common is horizontal transfer like retroviral genes being co-opted? syncyctin for example.

    [CZ: Definitely, these can be important. How common they are isn't yet clear.]

  4. Keith
    May 5, 2014

    Basil: A potential problem with your thesis is that there is no evolutionary pressure in primitive microbes to evolve genes that would later benefit a tiger hunting its prey, or an ant building a tunnel.

    • Basil Hall
      May 8, 2014

      Hi Keith, Microbes would not have to develop genes as they are already present as are all the genes during the embryology of a single individual of a single species.

      The vast majority of genetic material in all species is non-coding and I view this as store of genes that have been turned off. Extant microbes are going nowhere and it is important that they do not because they have a role in the corporate body of LIFE. Loss of genes at this level does not matter as long as the genes that encode for the form and function of the microbe are still present.

      If you read my “Letter to the editor” below you will appreciate from where I am coming.

      https://sites.google.com/site/basilhughhall/life-25

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