A Crack in Creation: Gene Editing and the Unthinkable Power to Control Evolution

Chapter 3 traces the crucial developments in CRISPR research that ultimately led to its transformation into a gene-editing tool. Doudna and Sternberg begin by establishing the collaborative nature of scientific discovery, using Doudna’s first laboratory experience studying papaya fungus as an illustration of how individual contributions build upon each other to create significant breakthroughs.

The authors explain that by 2010, scientists understood CRISPR provided bacteria with adaptive immunity against viruses, but many fundamental questions remained unanswered. Doudna’s team needed to determine how bacteria could extract and integrate DNA segments from viral genomes, how CRISPR RNA molecules were produced and processed within cells, and most crucially, how RNA could pair with viral DNA to trigger its destruction.

To address these questions, Doudna’s laboratory conducted extensive biochemical research on various CRISPR-associated (Cas) proteins. Working with two bacterial species, Escherichia coli and Pseudomonas aeruginosa, they discovered multiple proteins involved in DNA and RNA processing. The protein Cas1 helped insert viral DNA snippets into the CRISPR array, while Cas6 methodically sliced long CRISPR RNA molecules into shorter segments that could target viral DNA.

The authors detail how research revealed increasing complexity in CRISPR systems. What scientists initially thought was a single immune system turned out to include multiple variations, with different types and subtypes emerging as more bacterial and archaeal genomes were sequenced.