Genes Aren’t Blueprints, They’re Switches

| By on Endless Forms Most Beautiful

This summer BioLogos hosted the Evolution & Christian Faith Conference.  We heard lectures from a number of terrific speakers, including Ard Louis, Professor of Theoretical Physics at Oxford University.  His lecture was titled, “Randomness and other Metaphors in the Theory of Evolution.”  I encourage you to watch the entire talk, but in case you don’t have 45 minutes to spare (and at least that many more to sit and cogitate after that!), here’s one of the many gems he shared: genes aren’t blueprints; they’re switches.

In this clip, Ard introduces three conundrums of biology.  He points out that we share an astounding number of genes with other animals (96% with chimps), but we obviously look quite different.  Not only that, but some simple organisms--like the water flea or rice--have many more genes than we do, which is counterintuitive.  And finally, there are many different kinds of cells (e.g. heart cells, brain cells, muscle cells, fat cells) in our bodies, but they have exactly the same DNA.  How can this be?

Or stated another way,

  1. Why do different organisms share so many genes?  
  2. Why does the number of genes correlate so poorly with the biological complexity?
  3. Why are the cells in our body so different, if they all have the same DNA?

These do indeed seem like conundrums, and as a cell biologist I’ve spent some time thinking especially about the last one.  But Ard points out that perhaps we’ve been using the wrong metaphor.  We tend to think about genes as blueprints--as architectural drawings.  But that can’t quite be true because the same DNA makes all the types of cells in your body look different, and some very big drawings (rice genome) give rise to relatively simple organisms (rice) and vice versa.

To help answer the question, Ard plays part of a 2-minute “What is Evo-Devo?” video produced by Scientific American.  Host Christopher Mims uses the analogy of a power strip to illustrate how some genes act as master switches: flipping the switch controls the behavior of a number of other genes that are “plugged in.”

Genetic switches are well known from the field of developmental biology, which seeks to understand how an organism grows from a fertilized egg cell into an adult.  But switches are also important for determining how changes in morphology (body shape) can occur--the “evo” part.  So evolution and development are linked.  As Mims puts it, “Want to grow a body part, or develop?  Hit the master switch.  Want to change a body part to fit a different need, or evolve?  Mix up the plugs.”

The Understanding Evolution project at Berkeley has some great material on Evo Devo, if you’d like to read more.

Next time we’ll look at another metaphor that Ard unpacked in his talk.




Applegate, Kathryn. "Genes Aren’t Blueprints, They’re Switches" N.p., 20 Oct. 2015. Web. 20 March 2018.


Applegate, K. (2015, October 20). Genes Aren’t Blueprints, They’re Switches
Retrieved March 20, 2018, from /blogs/kathryn-applegate-endless-forms-most-beautiful/genes-arent-blueprints-theyre-switches

About the Author

Kathryn Applegate

Kathryn Applegate is Resources Editor at BioLogos. She received her PhD in computational cell biology at The Scripps Research Institute in La Jolla, Calif. At Scripps, she developed computer vision tools for analyzing the cell's infrastructure, the cytoskeleton. Kathryn joined the BioLogos staff in 2010.

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