Radiolab – Update: CRISPR

Date: February 24, 2017
Hosts: Jad Abumrad, Robert Krulwich
Key Contributors: Carl Zimmer, Jennifer Doudna, Beth Shapiro, Kevin Esvelt, Soren Wheeler, Molly Webster

Episode Overview

This episode of Radiolab revisits one of the most transformative discoveries in modern biology: CRISPR, a gene-editing technology with the potential to reshape life itself. The hosts reflect on the explosion of CRISPR news and research since their first episode, discuss ethical quandaries, recent landmark experiments, and the astonishing promise—as well as dangers—of tools that could let humanity rewrite evolution.

The program is part catch-up, part philosophical debate, and part news update, featuring discussions with scientists and science writers at the cutting edge of CRISPR research.

Key Discussion Points and Insights

1. Origin and Mechanism of CRISPR

[02:13]–[18:19]

• Discovery:
  • Scientists noticed repeated DNA sequences of unknown purpose in E. coli in 1987.
  • Carl Zimmer and Jennifer Doudna explain how researchers eventually realized these "blurp repeats" (CRISPRs) were part of a bacterial defense mechanism, storing viral DNA snippets as "mugshots" to recognize and destroy future viral invaders.
    • Jennifer Doudna: “You could actually program it to cut DNA and just like this molecular scissors and I can just program it and it cuts DNA wherever I want.” [17:50]
• Gene Editing Tool:
  • CRISPR/Cas9 system allows for highly precise, cheap, and universally applicable genetic engineering.
  • Past genetic editing tools were expensive, imprecise, and slow—now, costs have dropped from ~$5,000 to ~$75.

2. Potential and Hype

[20:12]–[21:59]

• Hosts and guests imagine extreme possibilities:
  • Reviving extinct species (e.g., “turn a chicken into a dinosaur” [20:28], “CRISPR out… elephant and put in woolly mammoth” [20:53]).
  • “Designer” animals and humans (e.g., making taller children, stronger muscles [21:08]).
• Carl Zimmer grounds expectations: making “winged pigs” is evolutionarily implausible, but real changes in existing species are possible.

3. Ethical Concerns and Social Implications

[22:17]–[27:15]

• The debate over “designer babies” and germline editing:
  • Editing embryos would create permanent, heritable genetic changes.
    • Jennifer Doudna: “That is a change to the DNA that will be passed on to their children and their children's children and their children’s children’s children.” [25:54]
  • The issue of consent: making genetic decisions for the unborn and future generations.
    • Jad Abumrad: “Consent becomes a real issue.” [26:05]
• Notable Moment: Chinese researchers edited non-viable human embryos using CRISPR, sparking international debate.

4. What Happens When Technology Leaps Ahead?

[27:27]–[32:24]

• The China embryo experiment revealed the CRISPR process is still error-prone (success in only 28 out of 86 embryos [29:09]), but this is expected to change as the technology improves.
• Comparison to IVF: initial controversy, now normalized; raises concern that germline gene editing could follow a similar path to social acceptance.
  • Carl Zimmer: “If we really are concerned about what we’re doing to the human gene pool, you know, it’s already here.” [30:14]

5. CRISPR Goes Mainstream and Scientific Landmarks

[33:00]–[38:00]

• CRISPR is now being used in crops, medicine, basic research, and livestock.
  • Notable anecdote: Even Jennifer Lopez is starring in a CRISPR-based TV drama! [33:04]
• Medical advances:
  • Early success in using CRISPR to treat muscular dystrophy in mice, resulting in dramatic muscle strength improvements. [34:44]
  • Human clinical trials are now beginning—e.g., in cancers, using CRISPR-edited immune cells to fight tumors [35:56].
  • Massive patent battles between teams led by Jennifer Doudna (UC Berkeley) and the Broad Institute (MIT/Harvard) over who owns the rights to CRISPR’s use. [36:42]

6. Alternative Applications and the “Gene Drive” Concept

[37:58]–[45:11]

• Antibiotic Alternative:
  • CRISPR could act as a targeted bacterial assassin, killing deadly pathogens without affecting others.
  • Soren Wheeler: “You would actually take a pill that was filled with CRISPR, and then it would go out and it would fight bacteria that is attacking your body.” [38:17]
• Gene Drive—the Scariest and Wildest Application:
  • Kevin Esvelt describes a way to engineer not just individuals but entire species, by passing CRISPR and its edit “instructions” down through generations (gene drive).
  • Could eradicate malaria by altering mosquito populations, but carries profound risks to ecosystems if something goes awry.
  • Kevin Esvelt: “What if we could encode CRISPR in the genome? … Program the genome to do genome editing on its own?” [40:13]
  • Esvelt: “This gene is going to spread like wildfire through the entire wild population. See, you don’t change just one mosquito… You change all of those insects, probably everywhere in the world.” [43:42]

7. Escalating Ethical Stakes and the Problem of Consent

[45:47]–[48:22]

• Editing an embryo is already contentious because it’s done without that individual’s consent; gene drive could make irreversible changes to entire populations, including untold future generations, without their knowledge or permission.
  • Jad Abumrad: “Now you’re doing it without the consent of that unborn thing and all future generations of that unborn thing. And so the consent issues just become like...unfathomable.” [48:08]
  • Robert Krulwich: “...with this gene drive, in the act of choosing it for yourself… you choose it for an uncountable number of others who do not have the choice.” [48:22]

Notable Quotes & Memorable Moments

• Carl Zimmer:

  • “These attackers, do we know what one of them looks like?”
    – Jennifer Doudna: “It actually looks, I would describe it a little bit like a clamshell, sort of imagine Pac-Man, but kind of misshapen and rough.” [12:09]
  • On CRISPR’s universality: “You can use the same CRISPR system on anything.” [17:20]

• Jennifer Doudna:

  • “I literally had—you know, the hairs on the back of my neck were standing up—just processing the fact that this thing exists, you know, and that you could actually program it to cut DNA and… it cuts DNA wherever I want.” [17:50]

• Kevin Esvelt:

  • “Let me tell you, there is nothing like the sheer elation of discovery… This is the end of malaria… And then I started thinking, but, but, but, but…what if something goes wrong?” [00:19 & 45:15]
  • “What if we could encode CRISPR in the genome? … Program the genome to do genome editing on its own?” [40:13]
  • “Without any human assistance, CRISPR will cut the original version and copy over the change.” [42:44]
  • “One person [could] decide to change the local or possibly the global environment. And that’s… ethically problematic, right?” [46:42]

• Robert Krulwich (on ethics):

  • “I don’t know where the sacred begins and ends anymore on that particular turf… There's an angelic side to being human and there's a very, very dark side… That future will include the imaginations, both light and dark, of humans. And that will be new in the world.” [23:08–24:22]

• Jad Abumrad:

  • “I’m a little bit haunted by the thing you said, which is that when it’s not dangerous anymore, what will we do? And I’m afraid we’ve already answered that question.” [31:51]
  • “Now you’re doing it without the consent... of all future generations... The consent issues just become, like, unfathomable.” [48:08]

Timeline of Key Segments

• 00:19–18:19: The mechanism and discovery of CRISPR; explanation by Carl Zimmer and Jennifer Doudna.
• 20:12–21:59: The science fiction possibilities and the line between excitement and caution.
• 22:17–27:15: The “designer baby” debate, China’s controversial embryo experiment, and the problem of heritable change.
• 27:27–32:24: Discussion of precaution, humanity already crossing lines (IVF precedent), and personal/cultural acceptance.
• 33:00–38:00: CRISPR in pop culture, medicine (cancer, muscular dystrophy), agriculture, and massive patent fights.
• 37:58–41:41: CRISPR as a new kind of antibiotic; introduction to gene drive.
• 41:46–45:11: Gene drives’ mechanism and the possibility (and risk) of editing entire species.
• 45:47–48:22: The ultimate ethical challenge: gene drive, consent, and changes at the species level.
• 49:11+: Episode wrap-up and credits.

Summary

“Update: CRISPR” is a whirlwind tour through one of the most consequential stories in biology. The episode clearly outlines not just how CRISPR works and its rapidly expanding applications, but also the ethical, social, and philosophical questions it forces us all to confront. With its lively, sometimes humorous tone, Radiolab makes complex molecular biology and bioethics accessible, memorable, and urgent. The episode closes with the realization that CRISPR’s potential is limited only by our collective imagination and restraint—and now, as the technology races ahead, humanity must decide how (or whether) to steer it.