WEBVTT - Gene Drives, GMO Pests, and Avoiding Extinction 0:00:00.160 --> 0:00:07.160 Brought to you by Toyota. Let's go places. Welcome to 0:00:07.360 --> 0:00:16.079 Forward Thinking. Hello, and welcome to Forward Thinking, this podcast 0:00:16.160 --> 0:00:18.759 that looks at the future and says, rescue me from 0:00:18.800 --> 0:00:22.120 me and all that I believe. I'm Lauren Volgabon and 0:00:22.239 --> 0:00:25.200 I'm Joe McCormick, and our regular host Jonathan Strickland is 0:00:25.239 --> 0:00:27.760 not with us today. He is still out on vacation. 0:00:28.400 --> 0:00:32.400 He's having lovely adventures in his absence. We went on 0:00:32.479 --> 0:00:36.199 a very short Billy Corgan impersonation to kick there, but 0:00:36.840 --> 0:00:40.200 that's no, was not recording that. I kind of hope 0:00:40.200 --> 0:00:42.159 he was. It was really delightful. Both of you do 0:00:42.200 --> 0:00:48.239 a really good smashing pumpkins. Anyway. Yeah, so today we're 0:00:48.240 --> 0:00:53.120 gonna be talking about a fascinating topic in genetics. Yes, 0:00:53.200 --> 0:00:55.200 but we want to get there in a kind of 0:00:55.280 --> 0:00:59.319 roundabout way by talking about islands. Yeah. We want to 0:00:59.360 --> 0:01:03.360 get there via the Galapagos. Have you ever been to 0:01:03.360 --> 0:01:05.640 the Galapagos? I have not, have you No, I haven't, 0:01:05.680 --> 0:01:07.959 But I want to go there someday. I know. It's lovely, 0:01:08.040 --> 0:01:11.120 it's it's a I mean, there's so many things there 0:01:11.160 --> 0:01:13.880 that you literally cannot find anywhere else, and not like 0:01:14.000 --> 0:01:17.680 restaurants like like beautiful wildlife. Yeah, I know, the restaurants 0:01:17.680 --> 0:01:19.920 seen there is probably not not what people go for. 0:01:20.520 --> 0:01:23.759 I don't think it is now. Yeah, so you're probably familiar, 0:01:23.800 --> 0:01:25.720 but just in case you're not. The Galapagos or a 0:01:25.800 --> 0:01:29.480 group of islands, or more accurately, a volcanic archipelago in 0:01:29.520 --> 0:01:33.000 the Pacific Ocean about about a thousand kilometers off the 0:01:33.040 --> 0:01:36.520 west coast of Ecuador, right along the equator. I think 0:01:36.560 --> 0:01:40.600 it actually straddles the equator. Yeah, yeah, and the Galapagos 0:01:40.720 --> 0:01:44.640 appear to have been mostly uninhabited before the Spanish visited 0:01:44.680 --> 0:01:48.280 in the sixteenth century by humans that is. Yeah. The 0:01:48.440 --> 0:01:51.680 glaucost Islands are situated more or less smack in the 0:01:51.680 --> 0:01:56.040 middle of these three conjoining tectonic plates and thus three 0:01:56.080 --> 0:01:59.320 different ocean currents, meaning that over the millennia, lots of 0:01:59.360 --> 0:02:02.000 credits from all over the world have wound up there, 0:02:02.000 --> 0:02:05.240 and the ones that stayed and reproduced branched off from 0:02:05.280 --> 0:02:08.800 their ancestors due to the unique living conditions and uh 0:02:09.040 --> 0:02:12.000 and separation from the general population. Yeah, and for this 0:02:12.080 --> 0:02:15.640 reason today the Galapagos I think are mainly known for 0:02:15.720 --> 0:02:18.760 their wildlife. That that's why people mostly want to go 0:02:18.919 --> 0:02:21.640 to this place. Yeah, so you've got, for example, the 0:02:21.720 --> 0:02:25.640 endemic Galapagos penguin, the Galapagos giant tortoise, and there are 0:02:25.639 --> 0:02:28.640 a few subspecies of that, like the saddleback tortoise and 0:02:28.639 --> 0:02:32.960 the dome tortoise, and then of course those smug, insufferable 0:02:33.040 --> 0:02:38.240 marine iguanas. Did did a marine iguana from Galapacos? Like? Wrong? 0:02:38.360 --> 0:02:40.760 You in your past? You know, I would never advise 0:02:40.800 --> 0:02:44.240 anybody treat them with anything but the utmost respect for nature. 0:02:44.280 --> 0:02:47.120 But just look at their faces. They just look like jerks. 0:02:47.280 --> 0:02:49.799 They do you sitting on those rocks, so they look 0:02:49.840 --> 0:02:53.120 really proud and slappable. Yeah, there's something about them. No, 0:02:53.280 --> 0:02:55.799 do not slap an iguana. Never slap an iguana. Why 0:02:55.840 --> 0:02:59.079 would you do that? The Galapagos. So yeah, so they've 0:02:59.120 --> 0:03:01.399 got they've got all these animals that are very beautiful 0:03:01.480 --> 0:03:04.840 and unique and and iconic in many ways. For one reason, 0:03:04.880 --> 0:03:08.440 I think because the Galapagos were, uh, this archipelago is 0:03:08.520 --> 0:03:11.200 one of the places that Charles Darwin stopped on his 0:03:11.400 --> 0:03:14.360 voyage on the h MS vegal famously. Yes, yeah, and 0:03:14.400 --> 0:03:16.800 so I think for that reason, they've become sort of 0:03:16.840 --> 0:03:21.079 emblematic of animal evolution and ecology in many ways since then. 0:03:21.200 --> 0:03:23.400 And like I said, I've never been, but I've always 0:03:23.400 --> 0:03:27.360 heard that because of the lack of large natural predators 0:03:27.360 --> 0:03:30.320 on the island, many of its animals are just very 0:03:30.360 --> 0:03:34.040 friendly chill. Yeah, they're they're fine basically with humans hanging 0:03:34.040 --> 0:03:36.600 out around them. Yeah, and they'll allow you to approach 0:03:36.680 --> 0:03:40.960 them without running away. So so that can be very 0:03:40.960 --> 0:03:46.440 wonderful if you are a peaceful, conservation minded ecological tourists 0:03:46.440 --> 0:03:48.560 who wants to visit the island and see some animals. 0:03:48.840 --> 0:03:51.480 Not so great for the animals if you are, say 0:03:51.200 --> 0:03:54.200 a pirate or a whaler or something that wants to 0:03:54.280 --> 0:03:56.200 kill a tortoise and eat it for its meat which 0:03:56.280 --> 0:03:59.080 has figured into the island's history, or or save it 0:03:59.160 --> 0:04:03.160 for or harvested for its beautiful shell or et cetera. Sure, exactly. 0:04:03.240 --> 0:04:05.240 So these days the glopacos are there's sort of a 0:04:05.280 --> 0:04:10.920 popular wildlife and conservation tourist destination, but the archipela goes. 0:04:11.120 --> 0:04:15.680 Beautiful and fascinating endemic species aren't the only critters on 0:04:15.680 --> 0:04:19.280 this island group today. Yeah, because if you know anything 0:04:19.440 --> 0:04:25.279 about sea travel, especially sea travel in prior centuries, humans 0:04:25.360 --> 0:04:28.680 weren't the only things on these ships. Right. There is 0:04:28.720 --> 0:04:31.400 a rodent problem, or has been a rodent problem in 0:04:31.440 --> 0:04:35.960 the Galapagos, And so according to the Galapagos Conservancy, the 0:04:36.120 --> 0:04:40.160 brown rat Rattus norvegicus and the black rat Ratus ratus. 0:04:40.320 --> 0:04:43.360 They were introduced to the Glapacos probably in the seventeenth 0:04:43.480 --> 0:04:47.520 or eighteen centuries by seafaring visitors like whalers and privateers. 0:04:47.560 --> 0:04:50.480 And as you alluded to, this is not an unusual story. 0:04:50.839 --> 0:04:54.680 Wherever humans go, various rodents tag along with us. There's 0:04:54.680 --> 0:04:56.400 sort of like a you know when you see a 0:04:56.480 --> 0:04:59.440 shark swimming swimming and it's got those little things hanging 0:04:59.440 --> 0:05:01.159 onto the body on side of it, and they just 0:05:01.240 --> 0:05:03.960 go along with it. Yeah, yeah, Or the barnacles that 0:05:04.000 --> 0:05:06.679 live on whales that whales sometimes use as big battering 0:05:06.760 --> 0:05:09.240 rams and whale battles. Yeah. So if we're the shark, 0:05:09.400 --> 0:05:12.360 those things are rodents, they just come along with us. Yeah, 0:05:12.680 --> 0:05:17.040 they're just hanging out. Because humans create a lot of trash. 0:05:17.080 --> 0:05:19.159 I think that actually is one of the reasons. But 0:05:19.960 --> 0:05:23.520 so like many other cases where organisms are introduced by 0:05:23.600 --> 0:05:27.760 humans to new ecosystems that haven't evolved to accommodate them, 0:05:27.760 --> 0:05:31.560 they haven't always been there. The native organisms can really suffer, 0:05:32.120 --> 0:05:35.080 and this has been the case over over the centuries 0:05:35.080 --> 0:05:39.320 with introduced rats and mice in the Galapagos. Many native organisms, 0:05:39.400 --> 0:05:44.000 especially birds and reptiles, have been severely threatened by these rodents, 0:05:44.000 --> 0:05:46.159 which tend to prey on their eggs and they're young. 0:05:46.480 --> 0:05:48.120 We've talked a bunch of times before in the show 0:05:48.160 --> 0:05:50.599 about these invasive species and then the kind of damage 0:05:50.640 --> 0:05:54.360 that they can do, because yeah, they nothing involved on 0:05:54.400 --> 0:05:57.720 that island to protect itself from this sort of threat exactly. 0:05:57.800 --> 0:06:01.039 So the Galapagos giant tortoise is one example. So the 0:06:01.080 --> 0:06:04.240 giant tortoise has been severely threatened on multiple islands by 0:06:04.279 --> 0:06:08.760 introduced animals, including rats, for one thing, though historically we 0:06:08.800 --> 0:06:11.279 would be remiss if we didn't also mention, as I 0:06:11.279 --> 0:06:13.839 alluded to a minute ago, the role humans played in 0:06:13.920 --> 0:06:19.479 more directly reducing those tortoise populations themselves through for example, hunting. 0:06:19.960 --> 0:06:21.320 And I don't know whether you'd say this is a 0:06:21.320 --> 0:06:25.120 direct or indirect. I guess indirect through habitat destruction. So 0:06:25.240 --> 0:06:28.360 the tortoises eggs and their hatchlings have been preyed upon 0:06:28.440 --> 0:06:31.320 by animals like rats, especially rats, so badly that on 0:06:31.360 --> 0:06:35.080 the island of pin Zone. Scientists believe that until just 0:06:35.200 --> 0:06:37.840 a couple of years ago, there had been no new 0:06:37.960 --> 0:06:43.160 tortoise hatchlings in about a hundred and fifty years. Yeah, exactly. 0:06:44.320 --> 0:06:47.760 So conservationists did come up with plans for ways to 0:06:47.760 --> 0:06:50.480 get around that, and that some of their plans actually 0:06:50.480 --> 0:06:54.799 did succeed. For example, uh decades old conservation efforts focused 0:06:54.839 --> 0:06:59.440 on breeding tortoises in captivity and keeping them there until 0:06:59.560 --> 0:07:02.400 the young tortoises were about four or five years old, 0:07:02.560 --> 0:07:05.159 at which point they became too large for the rats 0:07:05.200 --> 0:07:07.479 to prey on them. Referred to in the literature as 0:07:07.520 --> 0:07:13.240 being quote rat proof, rat proof tortoises, thank you, scientists. 0:07:14.040 --> 0:07:16.239 You'd think the shell would make them always rat proof, 0:07:16.240 --> 0:07:18.280 but I guess rats are crafty. I guess. Yeah. Well, 0:07:18.320 --> 0:07:21.120 and and when the tiny little baby baby tortoises are 0:07:21.200 --> 0:07:23.840 are you know, too small or I don't know, as 0:07:24.800 --> 0:07:27.840 I don't want to imagine this. It's very sad, but 0:07:27.840 --> 0:07:31.480 but yeah, so that did help. But even with this 0:07:31.520 --> 0:07:34.360 measure in place, the tortoise eggs would be threatened in 0:07:34.400 --> 0:07:38.400 the wild. So the problem was bad enough that conservationists 0:07:38.400 --> 0:07:41.560 trying to save the tortoises, began a program to eradicate 0:07:41.600 --> 0:07:46.320 the invasive rats in through mass poisoning with rat bait 0:07:46.480 --> 0:07:50.720 essentially okay poison, but so far it does seem to 0:07:50.760 --> 0:07:54.160 have worked. In January there was a letter to Nature 0:07:54.240 --> 0:07:57.760 where a group of scientists and conservationists confirmed that in 0:07:57.840 --> 0:08:01.160 December of the previous year, so December twenty fifteen, ten 0:08:01.320 --> 0:08:05.280 saddleback giant tortoise hatchlings had been found on pin Zone Island, 0:08:05.280 --> 0:08:08.320 and they believed that if they saw these, there must 0:08:08.360 --> 0:08:10.920 be more than they haven't found. And this was the 0:08:10.960 --> 0:08:13.400 first time hatchlings, as we said, have been observed in 0:08:13.440 --> 0:08:15.440 the wild and more than a d and fifty years, 0:08:15.840 --> 0:08:18.360 and so it suggests that the animals are finally able 0:08:18.640 --> 0:08:22.480 able to recover their population through natural breeding, not breeding 0:08:22.480 --> 0:08:25.280 in captivity. Yeah. Oh, that's that's wonderful. I have less 0:08:25.280 --> 0:08:29.400 good news to report, Yeah, yeah, just over the past 0:08:29.480 --> 0:08:32.480 month or so. Sadly, in May to June of six, 0:08:33.360 --> 0:08:36.200 news broke of of the first confirmed extinction of a 0:08:36.240 --> 0:08:39.600 bird species on Galapagos and the bird in question, which 0:08:39.640 --> 0:08:42.760 is the sun cuistal ball vermilion flycatcher. I'm not going 0:08:42.760 --> 0:08:44.680 to try the Latin because I didn't practice it before 0:08:44.720 --> 0:08:50.360 the show. Um they no, no birds of this type 0:08:50.360 --> 0:08:52.880 had been seen in the wild since seven so they 0:08:52.920 --> 0:08:55.640 were presumed to be extinct already. But but this this 0:08:55.720 --> 0:08:59.680 news comes after a genealogical and morphological review marked the 0:08:59.720 --> 0:09:02.280 bird as being its own species instead of just a 0:09:02.320 --> 0:09:06.719 subspecies as it was previously assumed to be. And what 0:09:07.120 --> 0:09:12.360 caused this extinction rats, I mean rats mostly um eating 0:09:12.440 --> 0:09:15.400 eating the eggs and also a parasitic fly that kills 0:09:15.520 --> 0:09:18.040 chicks when they do manage to grow to hatch. So 0:09:18.240 --> 0:09:21.520 bad times for this vermilion flycatcher. And they're really pretty, 0:09:21.640 --> 0:09:24.400 is the sad thing. They're just really a little scarlet 0:09:24.440 --> 0:09:28.280 colored birds anyway, sad though even we should always remember 0:09:28.280 --> 0:09:33.239 that even the ugly creatures should have deserved a good shake. Yeah. Absolutely, 0:09:33.800 --> 0:09:38.360 And now there are lots of other vermilion flycatchers of 0:09:38.440 --> 0:09:41.520 a various species and subspecies on the island, but lots 0:09:41.520 --> 0:09:45.320 of them are also in decline. And there's really interesting 0:09:45.360 --> 0:09:49.200 work being done in studying the birds individual island based 0:09:49.240 --> 0:09:54.120 adaptations because different islands within the archipelago have have have 0:09:54.200 --> 0:09:57.240 different environments and so you can really get into the 0:09:57.440 --> 0:10:01.000 genetics of how they adapted and broke off from each 0:10:01.000 --> 0:10:06.000 other within those populations. But it's a situation where researchers 0:10:06.000 --> 0:10:09.480 are basically scrambling to study the birds before they all disappear. 0:10:10.040 --> 0:10:12.080 They're they're hoping that a few more species can be 0:10:12.120 --> 0:10:16.480 and subspecies can be distinctified and identified, but they might 0:10:16.520 --> 0:10:19.400 not if we can't start controlling this rat population. Yeah, 0:10:19.480 --> 0:10:22.120 And so this is sort of a model of an 0:10:22.120 --> 0:10:27.280 issue that goes on around the world where small island 0:10:27.360 --> 0:10:31.640 populations of endemic animals are threatened by invasive species that 0:10:31.760 --> 0:10:35.559 humans bring along with them when they travel to these islands. So, 0:10:35.640 --> 0:10:39.280 in many cases, island wildlife conservation that's have been able 0:10:39.280 --> 0:10:43.440 to make some progress saving endemic species by eradicating invasive 0:10:43.480 --> 0:10:49.959 populations through totally conventional means poisoning, traps, etcetera. But none 0:10:50.000 --> 0:10:52.840 of those methods are ideal. When you lay out, you know, 0:10:53.080 --> 0:10:56.240 thousands of pounds of rat poison, you can just guess 0:10:56.280 --> 0:10:59.000 that that's not the thing you want to do most 0:10:59.320 --> 0:11:02.640 to the actually college, Yeah, or even traps, traps that 0:11:02.679 --> 0:11:05.839 other animals could blunder on into sure. And also these 0:11:05.880 --> 0:11:08.600 methods are just difficult to use, Like they can be 0:11:08.679 --> 0:11:12.880 expensive labor intensive to carry out. Uh, And so our 0:11:12.960 --> 0:11:16.200 question today, inspired by some recent stories in the news 0:11:16.320 --> 0:11:19.320 on this subject, is could we use a different method 0:11:19.880 --> 0:11:23.920 to try to eliminate invasive species on islands, a more 0:11:24.160 --> 0:11:29.760 forward thinking method. Possibly? The method in question is what's 0:11:29.840 --> 0:11:34.160 known as a gene drive. A gene drive? Right? Is this? 0:11:34.200 --> 0:11:39.160 Does this have to do with like donating denim? I think? 0:11:39.360 --> 0:11:41.120 I think when I was talking to my wife Rachel 0:11:41.160 --> 0:11:44.040 about this last night, she made the exact joke. High 0:11:44.080 --> 0:11:47.520 fives to Reachel. Yeah, not worded the same way, but 0:11:47.640 --> 0:11:51.800 it was. It was pants themed. So, uh, so what 0:11:51.880 --> 0:11:57.400 are gene drives? Well, let's sayward thinking it was pants themed. Sorry, 0:11:57.840 --> 0:12:01.839 sometimes so water gene Right, Well, let's say you want 0:12:01.840 --> 0:12:06.679 to spread an engineered gene throughout a population of animals. 0:12:07.320 --> 0:12:11.560 One commonly discussed example is that of a mosquito with 0:12:11.640 --> 0:12:15.760 a gene that prevents it from carrying the malaria parasite. Yeah, 0:12:15.760 --> 0:12:18.040 this is a thing that basically everyone can agree would 0:12:18.040 --> 0:12:20.480 be a plus exactly. I mean, it would be a 0:12:20.520 --> 0:12:24.960 life saving innovation on a massive, worldwide scale. If mosquitoes 0:12:25.040 --> 0:12:29.880 can't carry the malaria parasite and transmitted to humans, just 0:12:30.200 --> 0:12:33.120 enormous amounts of mortality and human misery around the world 0:12:33.120 --> 0:12:36.120 could be prevented. Yeah, if you if you do not remember, 0:12:36.240 --> 0:12:40.000 mosquitoes actually are the creature that kill the most humans, 0:12:40.440 --> 0:12:45.720 perhaps other than humans, every year indirectly by being the 0:12:45.760 --> 0:12:49.359 carriers of right. Yeah, I guess it's the malaria parasite. 0:12:49.400 --> 0:12:54.600 But yeah, and screw that parasite anyway, So it's really bad. 0:12:54.640 --> 0:12:56.880 But yeah, So if you can create a mosquito in 0:12:56.960 --> 0:13:00.520 the lab with a gene that says, sorry, malaria parasite 0:13:00.600 --> 0:13:04.439 can't survive in me, I won't transmit it. Uh, that 0:13:04.480 --> 0:13:06.640 would be great, But then you face another problem. Let's 0:13:06.640 --> 0:13:09.760 say you've created this mosquito. How do you get that 0:13:09.840 --> 0:13:13.959 mosquito to become the new mosquito to take over wild 0:13:14.040 --> 0:13:18.200 mosquito populations? Because just just releasing a single certainly a 0:13:18.240 --> 0:13:20.880 single creature, but even even a large number of creatures 0:13:20.880 --> 0:13:24.240 into the wild doesn't necessarily mean that their genetics will 0:13:24.320 --> 0:13:27.440 will propagate out over an entire population. Right, So let's 0:13:27.440 --> 0:13:30.720 look at what happens, I mean, how do sexually reproducing 0:13:30.760 --> 0:13:33.800 animals get their genes. Usually what happens is that a 0:13:33.800 --> 0:13:37.360 male and female mate and their offspring each received fifty 0:13:37.400 --> 0:13:42.000 percent of each parents genes, you get a recombinant mix 0:13:42.080 --> 0:13:44.960 of the two, mostly at random. So in the case 0:13:45.080 --> 0:13:47.960 of each gene location in the chromosomes, you have a 0:13:47.960 --> 0:13:51.440 fifty percent chance of inheriting the allele from your mom 0:13:51.600 --> 0:13:53.959 and a fifty percent chance of getting the allele from 0:13:54.000 --> 0:13:58.240 your dad. So if this anti malaria mosquito manages to mate, 0:13:58.679 --> 0:14:01.760 half of its offspring will carry the anti malaria gene, 0:14:02.120 --> 0:14:04.240 and are the ones that do carry it, only half 0:14:04.240 --> 0:14:07.720 of their offspring will carry it. Uh, there's this population 0:14:07.800 --> 0:14:12.360 genetics barrier to the spread of this anti malaria technology. 0:14:12.400 --> 0:14:15.360 And this is assuming that the trait has a neutral 0:14:15.400 --> 0:14:19.240 effect on survival and reproduction, or even confers an advantage 0:14:19.840 --> 0:14:22.840 so that the carrier mosquitoes have more offspring than the 0:14:22.880 --> 0:14:26.400 non carriers. Yeah, that's not guaranteed. It could be in 0:14:26.440 --> 0:14:30.680 some way detrimental to to the continuation of the species, 0:14:30.680 --> 0:14:34.080 to to reproducibility exactly. So if it's detrimental, we can 0:14:34.120 --> 0:14:38.040 probably expect it to dwindle and eventually disappear. Even if 0:14:38.120 --> 0:14:42.280 it's beneficial, it's only going to spread very slowly. It's 0:14:42.280 --> 0:14:45.440 gonna might become widespread among mosquitoes in the long run, 0:14:45.480 --> 0:14:48.040 but it will take a really long time and it's 0:14:48.040 --> 0:14:51.360 still not guaranteed. So if you want to be sure 0:14:51.560 --> 0:14:55.120 that it does become widespread among wild mosquitoes, you'd have 0:14:55.160 --> 0:15:01.000 to release just an absolutely gargantuan number of engineer mosquito 0:15:01.040 --> 0:15:04.160 individuals into the wild with this gene And that's not 0:15:04.200 --> 0:15:06.400 a great plan either. That doesn't sound like a fun 0:15:06.440 --> 0:15:09.640 way to spend my Saturday. Yeah, Like, if somebody comes 0:15:09.640 --> 0:15:11.600 to you and says, hey, we're going to release five 0:15:11.640 --> 0:15:16.400 hundred trillion engineered mosquitoes into a lot of help into 0:15:16.480 --> 0:15:20.640 your neighborhood, I feel like thanks. Uh. So this is 0:15:20.640 --> 0:15:23.080 where the gene drive comes in. So a gene drive 0:15:23.320 --> 0:15:27.720 is a system for biasing the inheritance of genes that 0:15:28.080 --> 0:15:32.400 is pretty simple, but the goal is towards altering an 0:15:32.600 --> 0:15:36.880 entire interbreeding population in a short amount of time. So 0:15:36.960 --> 0:15:39.760 at the microscopic level, the gene drive is literally just 0:15:39.960 --> 0:15:45.120 a heritable molecular mechanism, like a tiny molecule machine that's 0:15:45.160 --> 0:15:48.840 attached to your DNA that gets passed on from parent 0:15:48.920 --> 0:15:52.680 to offspring and ensures that a selected gene will be 0:15:52.720 --> 0:15:57.680 inherited with a near one certainty during sexual reproduction. Yeah, 0:15:57.680 --> 0:15:59.440 and well we'll talk a little bit about that mechanism 0:15:59.440 --> 0:16:01.320 in a minute. It but let's just let's just give 0:16:01.360 --> 0:16:03.440 give kind of an example of how this flows out 0:16:03.440 --> 0:16:07.040 to a population. Okay, So again, let's imagine that you 0:16:07.080 --> 0:16:09.320 want to use a gene drive to spread this anti 0:16:09.360 --> 0:16:13.800 malaria gene among a wild population of mosquitoes. We can assume, 0:16:13.800 --> 0:16:16.000 for the sake of an example, that the mosquito that 0:16:16.120 --> 0:16:19.520 mates produces four offspring that are able to reproduce into 0:16:19.520 --> 0:16:22.160 the next generation. This is not based on real mosquito 0:16:22.200 --> 0:16:24.440 browd numbers. I just picked a random number and it 0:16:24.520 --> 0:16:27.200 was four. Four is a nice easy one to multiply. 0:16:28.240 --> 0:16:31.280 So with half of them inheriting the gene, on average, 0:16:31.720 --> 0:16:34.680 one hundred percent of them or close to it will 0:16:34.720 --> 0:16:37.960 inherit the anti malaria gene. So now each of those 0:16:38.000 --> 0:16:42.640 four offspring I'll reproduce, and all of their offspring carried 0:16:42.640 --> 0:16:47.240 the anti malaria gene and the gene drive insurers continued inheritance. 0:16:47.240 --> 0:16:50.480 So then you've got sixteen and the next generation. Uh. 0:16:50.520 --> 0:16:53.000 And then if each of them has four offspring, you've 0:16:53.040 --> 0:16:55.920 got sixty four, and then two d and fifty six 0:16:56.360 --> 0:16:59.320 and then one thousand twenty four, and then four thousand, 0:16:59.400 --> 0:17:02.160 ninety six, and then sixteen thousand, three eight four, and 0:17:02.240 --> 0:17:06.080 by the sixteenth generation you have over a billion individual 0:17:06.200 --> 0:17:10.520 carriers of this gene. And so, okay, how this molecular 0:17:10.600 --> 0:17:13.080 mechanism works at a at a high level because I 0:17:13.119 --> 0:17:17.360 am not a geneticist. Um, it's it's actually a genetic 0:17:17.760 --> 0:17:21.119 power that is already seen in nature. There's uh this 0:17:21.200 --> 0:17:26.240 so called selfish genetic type of element of gene element. Okay, 0:17:26.280 --> 0:17:29.600 so these these genetic elements don't follow the usual law 0:17:29.600 --> 0:17:33.200 of averages of genetic inheritance inheritance um. When an egg 0:17:33.240 --> 0:17:37.040 is fertilized and one of the parents DNA contains a 0:17:37.080 --> 0:17:42.240 selfish element, that genetic bit targets the other parents parallel 0:17:42.600 --> 0:17:47.440 allele the other genetic bit and alters it. So zip 0:17:47.520 --> 0:17:51.119 zoom in this fertilized egg, you've got just about a 0:17:52.400 --> 0:17:58.080 heritable trait. The tricky bit here is taking the genes 0:17:58.119 --> 0:18:02.439 that make a selfish element and attaching them to the 0:18:02.480 --> 0:18:04.960 trait that you want to absolutely make sure it gets 0:18:05.000 --> 0:18:09.080 passed on. This this anti malaria trait um for for 0:18:09.080 --> 0:18:12.360 for example, and okay, science has been working on that 0:18:12.440 --> 0:18:15.040 part for over a decade, but it's been really rough 0:18:15.119 --> 0:18:19.000 going until our discovery of Crisper and cast nine came 0:18:19.040 --> 0:18:21.280 along over the past couple of years, and we did 0:18:21.320 --> 0:18:24.560 a whole episode about how that whole genetic toolkit works 0:18:24.640 --> 0:18:28.480 in April. The episode is called Editing Jeans with Crisper 0:18:28.520 --> 0:18:30.280 if you would like to go check it out. But 0:18:30.480 --> 0:18:34.520 in brief, crisper is another natural genetic process. It's it's 0:18:34.520 --> 0:18:38.320 part of some bacteria's adaptive immune system. So if a 0:18:38.320 --> 0:18:41.399 bacteria fights off a bacterium pardon me, fights off a 0:18:41.440 --> 0:18:45.439 particular virus that the crisper system will neatly snip out 0:18:45.640 --> 0:18:47.760 a wee bit of that viruss DNA is a sort 0:18:47.800 --> 0:18:50.320 of fingerprint or like a wanted poster, you can think 0:18:50.359 --> 0:18:53.600 of it and um. The system then attaches that snippet 0:18:53.600 --> 0:18:57.399 of d N d NA back into the bacterium's own DNA, 0:18:57.520 --> 0:18:59.280 so it keeps kind of like a catalog that it 0:18:59.280 --> 0:19:02.080 can refer back too. So if another virus with that 0:19:02.119 --> 0:19:04.440 bit of DNA ever comes a knocking at the bacterium's 0:19:04.480 --> 0:19:07.240 outer cell wall again, it will know immediately that the 0:19:07.320 --> 0:19:10.600 virus is bad news and can defend itself by dismantling 0:19:11.080 --> 0:19:13.920 part of the virus is d NA using a protein 0:19:13.960 --> 0:19:18.880 called CAST nine to do the manual labor. The bacterium 0:19:18.920 --> 0:19:22.680 can pass on it's wanted catalog to its offspring because 0:19:22.680 --> 0:19:24.800 it's part of its genetic code. So that is a 0:19:24.840 --> 0:19:30.280 super great way for bacteria to to live longer and better. 0:19:30.480 --> 0:19:33.520 It's a it's an amazing microscopic machine. It is. It is, 0:19:33.640 --> 0:19:36.800 and it's also super useful to us because one of 0:19:36.800 --> 0:19:39.639 the things that we've struggled with most in genetics classically 0:19:39.880 --> 0:19:43.879 has been how labor intensive and expensive it was to 0:19:44.000 --> 0:19:47.320 cut and paste to DNA together. But researchers figured out 0:19:47.320 --> 0:19:50.160 a way to apply the Crisper system to target basically 0:19:50.200 --> 0:19:54.160 any DNA they want, which means it's hella easy now 0:19:54.240 --> 0:19:57.560 to physically isolate and remove bits of genetic code and 0:19:57.600 --> 0:20:00.359 also to insert them into other bits of genetic Yeah, 0:20:00.400 --> 0:20:03.960 certainly relevant or relative to what it was before. Absolutely. 0:20:04.040 --> 0:20:07.320 So you you so you take this selfish element system 0:20:07.560 --> 0:20:10.520 and you combine it with our knowledge of the Crisper 0:20:10.520 --> 0:20:14.320 cutting pace system, and hazzah, you can pretty easily design 0:20:14.320 --> 0:20:16.800 a gene that will drive itself through a population just 0:20:16.840 --> 0:20:19.640 about as fast as that population can propagate. Yeah, and 0:20:19.800 --> 0:20:24.160 depending on the reproductive schedule of the organism in question, 0:20:24.880 --> 0:20:28.200 it can work with astonishing speed, like I've seen predictions 0:20:28.240 --> 0:20:31.719 that with a method method like this, scientists could stop 0:20:31.800 --> 0:20:35.159 the spread of malaria to humans within a couple of years. 0:20:36.600 --> 0:20:39.119 Whether so, whether or not these predictions are true, the 0:20:39.119 --> 0:20:42.920 gene drive is obviously an amazingly powerful tool for altering 0:20:43.040 --> 0:20:47.159 nature with a very low initial investment. But if we 0:20:47.200 --> 0:20:50.240 want to come back to the problem that we started 0:20:50.280 --> 0:20:53.199 discussing at the beginning of the episode, like invasive species 0:20:53.200 --> 0:20:56.439 on islands, how would you use a gene drive to 0:20:56.640 --> 0:20:59.080 fight a problem like this? Because in this case, the 0:20:59.119 --> 0:21:02.200 goal is not modifying an organism so that it does 0:21:02.320 --> 0:21:05.960 something different, like it doesn't become a disease vector. But 0:21:06.080 --> 0:21:09.640 the modification that we want is just something that would 0:21:09.640 --> 0:21:12.960 eradicate the species. Sure well, and in that case, really 0:21:13.000 --> 0:21:16.800 the modification that you want is something that does not reproduce. Right. 0:21:16.960 --> 0:21:19.840 So it's turns out it's not very hard to dream 0:21:19.920 --> 0:21:22.320 up a gene that, if delivered through a gene drive, 0:21:22.440 --> 0:21:26.000 can steer a population into extinction. In fact, it seems 0:21:26.040 --> 0:21:29.720 pretty easy. So let's say you have an island with 0:21:29.760 --> 0:21:33.359 a rat problem, and the rats are driving natural endemic 0:21:33.359 --> 0:21:37.040 species to extinction. Uh, here's the most common solution that 0:21:37.080 --> 0:21:40.240 scientists have come up with. You establish a gene drive 0:21:40.320 --> 0:21:43.440 for a trait that causes all of an animal's offspring 0:21:43.640 --> 0:21:47.919 to be male or or a vastly biased portion of 0:21:47.960 --> 0:21:51.639 them to be male. So imagine how this works on 0:21:51.640 --> 0:21:54.960 an island. With each generation, males make up a more 0:21:55.119 --> 0:21:59.919 disproportionate contingent of the total population, until eventually there are 0:22:00.119 --> 0:22:02.879 virtually no females for them to breed with, and the 0:22:02.960 --> 0:22:06.600 rats stop reproducing and disappear. Your rat problem on this 0:22:06.680 --> 0:22:11.480 island is gone. So there are some pros and cons 0:22:11.520 --> 0:22:15.600 to this method. Yeah, pros to this method. You don't 0:22:15.640 --> 0:22:18.159 need poison or traps. Don't need to dump thousands of 0:22:18.160 --> 0:22:20.639 pounds of rat poison out of helicopters all over the 0:22:20.800 --> 0:22:25.240 entire island and maybe accidentally poison other organisms and or 0:22:25.320 --> 0:22:27.800 set out traps that people have to collect and that 0:22:28.160 --> 0:22:30.040 you know, you maybe accidentally end up killing some of 0:22:30.080 --> 0:22:32.080 the animals you were trying to save getting your toe 0:22:32.160 --> 0:22:35.360 stuck in. Yeah, none of that. Good time. Another possible 0:22:35.400 --> 0:22:38.320 pro is that, so I mean a lot of the 0:22:38.359 --> 0:22:42.639 people who would be doing this eradication are probably animal lovers. 0:22:42.640 --> 0:22:45.200 It's not like they want the rats to suffer. They're 0:22:45.240 --> 0:22:49.159 just trying to keep native populations from going extinct. So 0:22:49.240 --> 0:22:51.800 this could be seen as a more humane way to 0:22:51.920 --> 0:22:55.800 eradicate invasive species. Instead of poisoning them killing them painfully, 0:22:56.160 --> 0:22:58.640 you just allow them to live out their lives without 0:22:58.760 --> 0:23:01.160 being able to make more are of them. They're very 0:23:01.240 --> 0:23:05.560 sexually frustrated lives. But but yes, other than that, it's 0:23:05.600 --> 0:23:09.199 it's definitely much more humane than poison. Yeah, I probably 0:23:09.240 --> 0:23:14.679 agree that that's true. But what if a reproduction prohibiting 0:23:14.760 --> 0:23:19.880 gene drive were to get loose in a non isolated population, 0:23:20.000 --> 0:23:22.000 Because the way it works on the island is it 0:23:22.080 --> 0:23:25.239 just keeps multiplying. This gene spreads through more and more 0:23:25.320 --> 0:23:29.080 the population until there's nothing left and then the rats 0:23:29.160 --> 0:23:33.399 die off. What if rats carrying this gene got to 0:23:33.440 --> 0:23:35.680 the mainland. What if they hitchhike on the sharks that 0:23:35.720 --> 0:23:40.160