Simon E. Fisher @ProfSimonFisher Tracing the complex connections between genes, brains, speech & language. Time flies like an arrow; fruit flies like a banana. Jul. 15, 2018 2 min read

Your genome is not a blueprint. A thread about misleading metaphors in science communication... 1/11

DNA is often referred to as a "blueprint for life". A blueprint is an architect plan, technical drawing or engineering design. Like a blueprint, DNA contains information to guide construction, in this case of a living organism. Beyond that, the analogy rapidly breaks down...2/11

...For blueprints, there's direct 1-to-1 mapping between each element of a design/drawing & its counterpart in the final constructed product. "DNA as a blueprint" implies that individual genes show 1-to-1 mapping with different parts of a body and/or its functions. Not so...3/11

...Many genes encode proteins. Their linear DNA sequence carries info for stringing together amino-acids (out of 20 different ones) in a particular order. This order determines how the string folds into a 3D shape. The shape determines the functions the protein carries out...4/11

...Your genome contains 20,000 protein-coding genes, with diverse roles; enzymes, hormones, receptors, structural proteins etc. They work together in complex networks, building & maintaining a living body of a myriad distinct cell types, with different genes switched on/off..5/11

...Molecular networks include genes that build proteins which regulate activity of other genes. Even hub genes don't show 1-to-1 mapping to tissue/organism outcomes e.g. the PAX6 gene doesn't direct eye development by itself & it also plays multiple other roles in the body...6/11

..Unlike a blueprint, we can't reverse engineer a genome from the appearance of an organism or the organisation of its tissues, however exquisitely we examine it. (Cells carry their own copies of the genome & so we can directly access the DNA, but that's a different issue.)..7/11

...Why isn't reverse engineering feasible? Because genomes guide the building of bodies through networks of gene activity interacting with other intrinsic & external factors via developmental cascades. This image, courtesy of @WiringTheBrain, elegantly captures the point...8/11

...To me, the blueprint metaphor has almost no explanatory value & is eerily reminiscent of the homunculus fallacy in accounts of vision. (There's no little person in your brain looking at patterns of light on your retina; & that would lead to an infinite regress.)...9/11

...@RichardDawkins & others have emphasized how genes are more like recipes than blueprints. I agree, but this still fails to fully capture key properties of how genomes encode biological info. Maybe, here we should move away from metaphors & just try to tell it as it is...10/11

...The reach of genetics is extending into many walks of life with potential impact on disease, health, society & education. Now, more than ever, it's crucial to communicate principles of gene coding to broad audiences in an accessible way, while avoiding broken metaphors. 11/11

You can follow @ProfSimonFisher.


Tip: mention @threader_app on a Twitter thread with the keyword “compile” to get a link to it.

Threader is an independent project created by only two developers. The site gets 500,000+ visits a month and our iOS Twitter client was featured as an App of the Day by Apple. Running this space is expensive and time consuming. If you find Threader useful, please consider supporting us to make it a sustainable project.