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I’m A Genetic Engineer. I’m Also a Fish.
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Uploaded: | 2024-04-18 |
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MLA Full: | "I’m A Genetic Engineer. I’m Also a Fish." YouTube, uploaded by SciShow, 18 April 2024, www.youtube.com/watch?v=zKKKJQ51aoE. |
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Horizontal gene transfer might not be the flashiest of names, but animals are using it to create genetic hybrids without a human in sight. Like frogs rocking the DNA snippets of snakes, and fish sharing antifreeze superpowers.
Hosted by: Savannah Geary (they/them)
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Sources:
https://www.britannica.com/science/horizontal-gene-transfer
https://www.nature.com/scitable/definition/eukaryote-eucariote-294/
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https://commons.wikimedia.org/wiki/File:Apple_tree_grafting_2.jpg
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https://tinyurl.com/ysxkp4ez
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https://tinyurl.com/3xnasumw
https://tinyurl.com/2s3hc2p3
https://tinyurl.com/2p9hp4w5
https://tinyurl.com/y9kwejjd
Hosted by: Savannah Geary (they/them)
----------
Support SciShow by becoming a patron on Patreon: https://www.patreon.com/scishow
----------
Huge thanks go to the following Patreon supporters for helping us keep SciShow free for everyone forever: Adam Brainard, Alex Hackman, Ash, Benjamin Carleski, Bryan Cloer, charles george, Chris Mackey, Chris Peters, Christoph Schwanke, Christopher R Boucher, DrakoEsper, Eric Jensen, Friso, Garrett Galloway, Harrison Mills, J. Copen, Jaap Westera, Jason A Saslow, Jeffrey Mckishen, Jeremy Mattern, Kenny Wilson, Kevin Bealer, Kevin Knupp, Lyndsay Brown, Matt Curls, Michelle Dove, Piya Shedden, Rizwan Kassim, Sam Lutfi
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#SciShow #science #education #learning #complexly
----------
Sources:
https://www.britannica.com/science/horizontal-gene-transfer
https://www.nature.com/scitable/definition/eukaryote-eucariote-294/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9555858/
https://www.merriam-webster.com/dictionary/prokaryote
https://www.merriam-webster.com/dictionary/conjugation
https://www.merriam-webster.com/dictionary/transposons
https://www.britannica.com/science/transposon
https://www.nature.com/articles/s41467-020-15149-4
https://pubmed.ncbi.nlm.nih.gov/30113080/
https://www.genome.gov/genetics-glossary/germ-line
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3068243/
https://doi.org/10.1016/j.tig.2021.02.006
https://www.sciencedirect.com/science/article/pii/S2214574523000329
https://www.britannica.com/plant/angiosperm
https://www.pnas.org/doi/10.1073/pnas.1319929111
https://www.fs.usda.gov/wildflowers/beauty/ferns/reproduction.shtml
https://www.britannica.com/plant/hornwort
https://www.ucl.ac.uk/taxome/jim/Mim/mallethyb05.pdf
https://www.nature.com/articles/nature13291
https://academic.oup.com/mbe/article/39/4/msac052/6563207?login=false
https://www.quantamagazine.org/how-genes-can-leap-from-snakes-to-frogs-20221027/?mc_cid=1fb1939045
https://www.quantamagazine.org/dna-jumps-between-animal-species-no-one-knows-how-often-20210609/
https://www.merriam-webster.com/dictionary/electroporation
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2975437/
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Image Sources:
https://www.gettyimages.com/detail/video/biological-engineering-gene-modification-gmo-genetically-stock-footage/817600658
https://www.gettyimages.com/detail/video/pseudomonas-aeruginosa-bacteria-stock-footage/1487338845
https://javalab.org/en/human_gene_transfer_en/
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https://www.inaturalist.org/observations/52228866
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https://commons.wikimedia.org/wiki/File:Apple_tree_grafting_2.jpg
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https://tinyurl.com/4z3hkxmr
https://commons.wikimedia.org/wiki/File:FishEggs.jpg
https://tinyurl.com/53s6uu4v
https://tinyurl.com/2vv29kse
https://tinyurl.com/ysxkp4ez
https://tinyurl.com/4a8ebs76
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https://tinyurl.com/y9kwejjd
Humans aren’t the only genetic engineers out there.
I mean, they might not understand either the concept of genetics or engineering, but plenty of other life forms can take a gene from the DNA of one organism, and get it into the DNA of another. Sometimes they even do it on purpose.
But maybe it’s more appropriate for me to call it by its more technical name: horizontal gene transfer. It’s why bacteria keep becoming resistant to the antibiotics we’re using to kill them. It’s why ferns survived the literal rise of sun-blocking trees.
And it may be why there’s a fish swimming around in the ocean right now, conjuring its inner Dr. Frankenstein. [♪ INTRO] Okay first off, let’s remember what a gene even is. It’s basically a set of instructions in your DNA, or any creature’s DNA, that tells the body to do a very specific thing.
Like, make this exact protein that goes on to do that exact job. And many of you might be familiar with vertical gene transfer, which is when genes are passed down to the next generation via offspring. This is how genes are typically transferred in plants, fungi, animals, and yes, even your parents.
But if vertical gene transfer is like giving your child an index card with grandma’s recipe for shepherd's pie… then horizontal gene transfer would be like handing that card to a stranger that you bumped into on the street. And in prokaryotes– our distant, usually single-celled cousins whose cells don’t have nuclei to house their DNA– it almost is that simple. For example, in a process known as transformation, a prokaryote may just stumble upon some loose genetic material and incorporate it, pocketing it like a five dollar bill from the street.
Or in conjugation, two prokaryotes may do something akin to open mouth kissing, which allows them to exchange genetic material. And sometimes, that genetic material is extra good at transferring from one organism to another because it’s a “jumping gene”. More formally called a transposon.
These genes can actually move around in a cell. Like, just up and take a stroll down the genome to find a new spot for themselves. And because of this mobility, transposons can mosey right across that open mouth kiss bridge, and nuzzle into other prokaryotic genomes too. another prokaryotic genome.
So horizontal gene transfer is easy peasy lemon squeezy for prokaryotes. It’s why antibiotic resistance is such an issue these days. But that doesn’t mean prokaryotes have a monopoly on the practice.
Prokaryotes can also transfer genes to eukaryotes, better known as life whose cells have nuclei. The group includes everything from single-celled amoebas, to you, to your overwatered houseplant. But eukaryotes can also transfer genes between each other.
Yes, even your overwatered houseplant. Hundreds of millions of years ago, ferns found themselves in a tricky situation. Angiosperms, or flowering plants, had recently evolved and were popping up all over the place and blocking out quality sunshine.
So the ferns were faced with a challenge: make do with what little sunshine they got from the shade, or die. But seemingly out of nowhere, a gene appeared in their DNA that let them thrive even without a ton of sunshine. It single handedly enabled ferns to live in the shade.
And once they had this advantageous gene, you can bet they passed it down to their kiddos through regular old vertical gene transfer. But ferns didn’t start with this gene. And given how key it was to their success, researchers wanted to know where it came from.
After analyzing forty plant genomes, the scientists found the shade-thriving gene in one other plant: hornworts. And when they dug a little deeper, they found that the ferns didn’t just happen to evolve a similar version of the hornworts’ gene. They took a copy for themselves, roughly 179 million years ago.
This was the first evidence of plant to plant horizontal gene transfer. But the big question was how it happened. Luckily, the researchers have pretty solid ideas.
See, ferns and hornworts aren’t like seeding plants, which make little armored seeds and send them on their merry way to break open and grow. Instead, they produce spores, which inevitably blow off and land in a moist location to germinate into gametophytes, which then release their own sperm and/or eggs into nearby puddles. The sperm then swim around until they find an egg to fertilize, to then grow into a new fern or hornwort.
So it’s a happy little pool of fern and hornwort sperm and eggs. But like a highschool coed lock-in, the researchers doubt everyone stayed nice and separated. In fact, this is the place where the genomes of the hornwort and fern are least defended and most prone to contact one another.
No cell wall chaperones around. So they hypothesize that one of these love puddles was the site of a little horizontal gene transfer between the two. If prokaryotes participate in horizontal gene transfer through metaphorical kisses, and ferns did it through slightly less metaphorical love puddles, then some other plants do it through hugs.
Really, really close hugs. The kind where you literally fuse together. Now, plants mixing genes together isn’t really a surprise on its own.
It happens a lot with hybridization, where the species are close enough relatives to cross pollinate and make baby plants that feature genes from both parents. But that’s noticeably different from the hijacking of a single gene like we saw with the ferns and hornworts. So witnessing a genetic exchange in the absence of cross pollination would be quite the surprise.
But one team of researchers out of Germany and Poland figured out a way to achieve this: the aforementioned plant hugs. Okay, they didn’t call them plant hugs. The more appropriate term is grafting.
So they grafted together two species of tobacco plants: tree tobacco and cigarette tobacco. And to see if the genomes combined, they made sure that the plants each had a different gene that made them resistant to a different antibiotic. If the resulting plant and its offspring were resistant to both antibiotics, then that would be evidence that the genomes did combine via horizontal gene transfer.
And that’s exactly what they found. But plants, you may have noticed, don’t play by the same rules animals do. Because while human genetic engineers can take a single gene from a spider and put it into a goat’s genome, you can’t sew a spider and goat together to get a “spoat” genome.
As cool as that would be. So you might think it’s impossible for one animal species to horizontally transfer a gene without human intervention. But, surprise!
It’s already happened, thanks to those jumping genes we discussed earlier. For example, one transposon called Bovine-B managed to snake its way into certain frog genomes from their natural predators: snakes. In an article published in the journal Molecular Biology and Evolution, researchers sequenced the DNA of several snakes, frogs, and other species to see how the snake Bovine-B gene was getting into frogs.
And they concluded that while it may start in snakes, the gene likely didn’t go directly into their prey. Instead it probably jumped first into something like a parasitic mite, and then into the frogs. That means that not only can horizontal gene transfer occur in animals, but it can even occur with a two step process.
From animal to animal vector to animal. And the crazy thing is that unlike most genes, Bovine-B doesn’t even seem to have any genetic benefit. Rather than being a positive mutation those first frogs kept around because it helped them survive, scientists think Bovine-B is popular solely because of how good it is at replicating and jumping.
But if you’re looking for something closer to that fern and hornwort example, we can talk about a jumping antifreeze protein, or AFP, gene. Antifreeze proteins are exactly what they sound like: proteins designed to stop ice crystals from forming in the body when it’s super cold. So if you’re a fish who frequents arctic or antarctic ocean waters, that would be a pretty good gene to have.
That means it isn’t too surprising to hear that both herring and smelts have this antifreeze protein. But like the fern and the hornwort, they’re both using the same gene. It’s a clear example of horizontal gene transfer.
And since the herring has eight copies of the gene while the smelt only has one, it’s pretty easy to figure out who the copycat was here. [Pst] It’s the one with fewer copies. And fish kinda reproduce like ferns, in that they get it on by releasing all their eggs and sperm into one shared, watery ecosystem. So it’s reasonable to think this AFP gene was horizontally transferred from the herring to the smelt at this point in their life cycle.
Unfortunately, it’s much easier to show that the horizontal gene transfer happened at all, rather than figure out how it happened. And given how rare horizontal gene transfer appears in life as complex as frogs or fishes, it can be difficult to set up experiments that can test what’s going on. But that doesn’t mean it’s impossible.
Compared to proverbial hugs and kisses, our last method of horizontal gene transfer sounds a lot less gentle. Because it involves a literal shock to the system. The method is called electroporation, and as the name suggests, it involves using electricity to create tiny pores in a cell.
Those temporary pores can then let materials pass through them, including DNA. So electroporation is a choice method for scientists who need to do things like add or remove genes from their mice or cell culture test subjects to figure out what exactly certain genes do. But if you think about it, the combination of stray DNA, developing cells, and electricity doesn’t only occur in the lab.
In fact, at this point we know that ocean water is full of sperm and egg cells, ripe for the modifying. Plus, since fish don’t clean up their scales or waste while swimming around, it’s equally well equipped with DNA, too. Now, while human mad scientists aren’t going around shocking the ocean to create a bunch of mutant animals, you know what might be?
Electric eels. Which for the record, are as much eels as they are mad scientists. But knowing this, researchers from Japan wanted to see if electric eels could cosplay as genetic engineers.
To test their hypothesis, they put a bunch of zebrafish larvae into some water, alongside snippets of DNA that provided a recipe for a specific protein that glows green under a blacklight. In other words, if the larvae managed to incorporate the gene into their own DNA, they’d wind up glowing. Then, the team let their electric eel feast upon a nearby goldfish.
In trying to shock its prey, the eel also wound up shocking the larvae. And they found that the electricity did cause electroporation in the zebrafish larvae, and compared to the control groups, more of those larvae did wind up glowing green. This means that hypothetically, wild electric eels that are just swimming around, minding their own business and trying to survive, could also be zapping free-floating DNA into unsuspecting ocean critters.
Which is a remarkable feat for organisms who can’t attend grad school or occupy a lab bench. In addition to that research, a separate scientist from Slovenia took this idea a step further by suggesting that lightning strikes could also facilitate horizontal gene transfer. Cue Mary Shelley rolling in her grave.
And cue me off to write a sequel to Frankenstein. Where the doctor is a giant sentient electric eel and he’s, like, making pointless animal hybrids using his own body. And while I work on that, real scientists can work out the actual practical applications.
Because thanks to horizontal gene transfer, one species' genomic trash or treasure could easily become… another species' genomic trash or treasure, too. Thanks for watching this episode of SciShow. And an extra special thanks to our President of Science: McLaren Stanley!
I will definitely not be emailing you my first draft of Frankenstein 2: The real modern Prometheus is a giant eel. Because we all value your support too much. [♪ OUTRO]
I mean, they might not understand either the concept of genetics or engineering, but plenty of other life forms can take a gene from the DNA of one organism, and get it into the DNA of another. Sometimes they even do it on purpose.
But maybe it’s more appropriate for me to call it by its more technical name: horizontal gene transfer. It’s why bacteria keep becoming resistant to the antibiotics we’re using to kill them. It’s why ferns survived the literal rise of sun-blocking trees.
And it may be why there’s a fish swimming around in the ocean right now, conjuring its inner Dr. Frankenstein. [♪ INTRO] Okay first off, let’s remember what a gene even is. It’s basically a set of instructions in your DNA, or any creature’s DNA, that tells the body to do a very specific thing.
Like, make this exact protein that goes on to do that exact job. And many of you might be familiar with vertical gene transfer, which is when genes are passed down to the next generation via offspring. This is how genes are typically transferred in plants, fungi, animals, and yes, even your parents.
But if vertical gene transfer is like giving your child an index card with grandma’s recipe for shepherd's pie… then horizontal gene transfer would be like handing that card to a stranger that you bumped into on the street. And in prokaryotes– our distant, usually single-celled cousins whose cells don’t have nuclei to house their DNA– it almost is that simple. For example, in a process known as transformation, a prokaryote may just stumble upon some loose genetic material and incorporate it, pocketing it like a five dollar bill from the street.
Or in conjugation, two prokaryotes may do something akin to open mouth kissing, which allows them to exchange genetic material. And sometimes, that genetic material is extra good at transferring from one organism to another because it’s a “jumping gene”. More formally called a transposon.
These genes can actually move around in a cell. Like, just up and take a stroll down the genome to find a new spot for themselves. And because of this mobility, transposons can mosey right across that open mouth kiss bridge, and nuzzle into other prokaryotic genomes too. another prokaryotic genome.
So horizontal gene transfer is easy peasy lemon squeezy for prokaryotes. It’s why antibiotic resistance is such an issue these days. But that doesn’t mean prokaryotes have a monopoly on the practice.
Prokaryotes can also transfer genes to eukaryotes, better known as life whose cells have nuclei. The group includes everything from single-celled amoebas, to you, to your overwatered houseplant. But eukaryotes can also transfer genes between each other.
Yes, even your overwatered houseplant. Hundreds of millions of years ago, ferns found themselves in a tricky situation. Angiosperms, or flowering plants, had recently evolved and were popping up all over the place and blocking out quality sunshine.
So the ferns were faced with a challenge: make do with what little sunshine they got from the shade, or die. But seemingly out of nowhere, a gene appeared in their DNA that let them thrive even without a ton of sunshine. It single handedly enabled ferns to live in the shade.
And once they had this advantageous gene, you can bet they passed it down to their kiddos through regular old vertical gene transfer. But ferns didn’t start with this gene. And given how key it was to their success, researchers wanted to know where it came from.
After analyzing forty plant genomes, the scientists found the shade-thriving gene in one other plant: hornworts. And when they dug a little deeper, they found that the ferns didn’t just happen to evolve a similar version of the hornworts’ gene. They took a copy for themselves, roughly 179 million years ago.
This was the first evidence of plant to plant horizontal gene transfer. But the big question was how it happened. Luckily, the researchers have pretty solid ideas.
See, ferns and hornworts aren’t like seeding plants, which make little armored seeds and send them on their merry way to break open and grow. Instead, they produce spores, which inevitably blow off and land in a moist location to germinate into gametophytes, which then release their own sperm and/or eggs into nearby puddles. The sperm then swim around until they find an egg to fertilize, to then grow into a new fern or hornwort.
So it’s a happy little pool of fern and hornwort sperm and eggs. But like a highschool coed lock-in, the researchers doubt everyone stayed nice and separated. In fact, this is the place where the genomes of the hornwort and fern are least defended and most prone to contact one another.
No cell wall chaperones around. So they hypothesize that one of these love puddles was the site of a little horizontal gene transfer between the two. If prokaryotes participate in horizontal gene transfer through metaphorical kisses, and ferns did it through slightly less metaphorical love puddles, then some other plants do it through hugs.
Really, really close hugs. The kind where you literally fuse together. Now, plants mixing genes together isn’t really a surprise on its own.
It happens a lot with hybridization, where the species are close enough relatives to cross pollinate and make baby plants that feature genes from both parents. But that’s noticeably different from the hijacking of a single gene like we saw with the ferns and hornworts. So witnessing a genetic exchange in the absence of cross pollination would be quite the surprise.
But one team of researchers out of Germany and Poland figured out a way to achieve this: the aforementioned plant hugs. Okay, they didn’t call them plant hugs. The more appropriate term is grafting.
So they grafted together two species of tobacco plants: tree tobacco and cigarette tobacco. And to see if the genomes combined, they made sure that the plants each had a different gene that made them resistant to a different antibiotic. If the resulting plant and its offspring were resistant to both antibiotics, then that would be evidence that the genomes did combine via horizontal gene transfer.
And that’s exactly what they found. But plants, you may have noticed, don’t play by the same rules animals do. Because while human genetic engineers can take a single gene from a spider and put it into a goat’s genome, you can’t sew a spider and goat together to get a “spoat” genome.
As cool as that would be. So you might think it’s impossible for one animal species to horizontally transfer a gene without human intervention. But, surprise!
It’s already happened, thanks to those jumping genes we discussed earlier. For example, one transposon called Bovine-B managed to snake its way into certain frog genomes from their natural predators: snakes. In an article published in the journal Molecular Biology and Evolution, researchers sequenced the DNA of several snakes, frogs, and other species to see how the snake Bovine-B gene was getting into frogs.
And they concluded that while it may start in snakes, the gene likely didn’t go directly into their prey. Instead it probably jumped first into something like a parasitic mite, and then into the frogs. That means that not only can horizontal gene transfer occur in animals, but it can even occur with a two step process.
From animal to animal vector to animal. And the crazy thing is that unlike most genes, Bovine-B doesn’t even seem to have any genetic benefit. Rather than being a positive mutation those first frogs kept around because it helped them survive, scientists think Bovine-B is popular solely because of how good it is at replicating and jumping.
But if you’re looking for something closer to that fern and hornwort example, we can talk about a jumping antifreeze protein, or AFP, gene. Antifreeze proteins are exactly what they sound like: proteins designed to stop ice crystals from forming in the body when it’s super cold. So if you’re a fish who frequents arctic or antarctic ocean waters, that would be a pretty good gene to have.
That means it isn’t too surprising to hear that both herring and smelts have this antifreeze protein. But like the fern and the hornwort, they’re both using the same gene. It’s a clear example of horizontal gene transfer.
And since the herring has eight copies of the gene while the smelt only has one, it’s pretty easy to figure out who the copycat was here. [Pst] It’s the one with fewer copies. And fish kinda reproduce like ferns, in that they get it on by releasing all their eggs and sperm into one shared, watery ecosystem. So it’s reasonable to think this AFP gene was horizontally transferred from the herring to the smelt at this point in their life cycle.
Unfortunately, it’s much easier to show that the horizontal gene transfer happened at all, rather than figure out how it happened. And given how rare horizontal gene transfer appears in life as complex as frogs or fishes, it can be difficult to set up experiments that can test what’s going on. But that doesn’t mean it’s impossible.
Compared to proverbial hugs and kisses, our last method of horizontal gene transfer sounds a lot less gentle. Because it involves a literal shock to the system. The method is called electroporation, and as the name suggests, it involves using electricity to create tiny pores in a cell.
Those temporary pores can then let materials pass through them, including DNA. So electroporation is a choice method for scientists who need to do things like add or remove genes from their mice or cell culture test subjects to figure out what exactly certain genes do. But if you think about it, the combination of stray DNA, developing cells, and electricity doesn’t only occur in the lab.
In fact, at this point we know that ocean water is full of sperm and egg cells, ripe for the modifying. Plus, since fish don’t clean up their scales or waste while swimming around, it’s equally well equipped with DNA, too. Now, while human mad scientists aren’t going around shocking the ocean to create a bunch of mutant animals, you know what might be?
Electric eels. Which for the record, are as much eels as they are mad scientists. But knowing this, researchers from Japan wanted to see if electric eels could cosplay as genetic engineers.
To test their hypothesis, they put a bunch of zebrafish larvae into some water, alongside snippets of DNA that provided a recipe for a specific protein that glows green under a blacklight. In other words, if the larvae managed to incorporate the gene into their own DNA, they’d wind up glowing. Then, the team let their electric eel feast upon a nearby goldfish.
In trying to shock its prey, the eel also wound up shocking the larvae. And they found that the electricity did cause electroporation in the zebrafish larvae, and compared to the control groups, more of those larvae did wind up glowing green. This means that hypothetically, wild electric eels that are just swimming around, minding their own business and trying to survive, could also be zapping free-floating DNA into unsuspecting ocean critters.
Which is a remarkable feat for organisms who can’t attend grad school or occupy a lab bench. In addition to that research, a separate scientist from Slovenia took this idea a step further by suggesting that lightning strikes could also facilitate horizontal gene transfer. Cue Mary Shelley rolling in her grave.
And cue me off to write a sequel to Frankenstein. Where the doctor is a giant sentient electric eel and he’s, like, making pointless animal hybrids using his own body. And while I work on that, real scientists can work out the actual practical applications.
Because thanks to horizontal gene transfer, one species' genomic trash or treasure could easily become… another species' genomic trash or treasure, too. Thanks for watching this episode of SciShow. And an extra special thanks to our President of Science: McLaren Stanley!
I will definitely not be emailing you my first draft of Frankenstein 2: The real modern Prometheus is a giant eel. Because we all value your support too much. [♪ OUTRO]