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

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