gene guns? 👀

botanyshitposts:

ooooo boy okay so 

the problem with gene editing in general isn’t the gene editing itself, but getting the gene into an organism in a way that it can modify the stuff inside of it. this is surprisingly difficult to do.

so in modern applications, we have stuff like CRISPR. CRISPR is essentially a modified viral structure. to back up even further here, viruses aren’t traditionally considered organisms so much as they’re considered molecular machines; a virus reproduces itself by injecting its own RNA (an offset of DNA that can be easily replicated by the cell) into a cell; this results in the cell integrating the invading RNA into the genome of the cell, where it then can be converted into proteins that make up more viruses. once the viruses become too numerous for the cell to handle, the cell literally explodes, and the viruses that burst out of the cell go to other cells and repeat the process. 

now, CRISPR doesn’t work exactly like that. CRISPR is comprised of a virus, yes, but instead of infecting a host with a terrible virus that kills cells and things, CRISPR uses the starting machinery- the stuff that cuts and pastes- plus whatever gene you want, and instead of an infection just introduces the modified genes into the cell’s genome, where after a number of tries, the cell might decide to integrate it fully and begin expressing it. i’m not educated enough on the exact mechanisms of CRISPR to explain it in any further detail here, but know as a clarification that you couldn’t really ‘catch’ a CRISPR ‘virus’; technically what CRISPR is based off of is a bacteriophage, witch is a simple virus that specifically infects bacteria, not humans. 

UPDATE/CORRECTION: ive been informed that CRISPR isn’t in fact a virus in and of itself, but rather a piece of genetic material isolated from the immune systems of bacteria, which preforms a variety of functions with RNA and DNA of the cell including, but not limited to, fighting viruses to an extent. 

so imagine this: your friend is in a manhole on a construction site. the ladder in the manhole is broken, and to free themselves, they’ll need to fix it with your help. to do this, you will have to help them modify the ladder by replacing a broken rung, so you get some supplies in a bucket to lower down to them. it’s very dark in the manhole, and they can’t see what they’re supposed to cut, so you first put in the bucket 1. a glow in the dark map to show them where the broken rung is on the ladder. then, you put in 2. a special pair of scissors to cut the old rung out. finally, you put in 3. a new rung. your friend already has glue because they’re just like that. you lure the bucket in with a rope, and using the supplies in the bucket your friend replaces the broken parts. your friend is pretty smart; sometimes, there are multiple rungs that are broken with all different instructions, and your friend can replace them all!

the bucket, and the things in the bucket, represent CRISPR and what it does; the only thing we change are the instructions on what to cut and the rung to replace it. (this was a rambling analogy that is completely unnecessary to answer the gene gun question but i wanted to learn about it and repeating it like that here helps me learn the topic so yeah.)

i’ve never used it myself, but i’ve been told that in plant applications, CRISPR physically manifests as a weird jelly that you load up with whatever fun stuff you want (the actual gene editing has to be done via another process in advance) and rub on the plant, and the machinery takes it from there. it’s really cool technology. 

now, here’s the thing. CRISPR is pretty new technology, too. it’s cheap, it’s effective, it’s very clean, and it doesn’t mess things up too much. 

now, before we had nice rad slime to put on things that would change an organism’s genome for us, we had people in the corn business in the mid-80s who wanted to genetically modify corn faster. so they did the normal, sane thing to do, which is to just fucking shoot the cells. like. with cell-sized bullets, bc fuck those guys.

so a ‘gene gun’ works like this: you got ur metal box equipped with an airsoft-rifle-like discharge, in the sense that it discharges a high-pressure air blast. you got ur DNA that u want put in the cells. you got ur cells, in plant contexts in the form of weird lumps of cells that can just regenerate into a full plant the same way a weed could fully regenerate from a single root, because plants are just like that. finally, you got ur nanoparticles, usually of a heavy element like gold or tungsten. 

you coat your heavy particles in the DNA in advance. u put them under the high-pressure air blast. under that, you put your poor plant cells that literally just want to live their lives. then, you turn on the gun, and it literally shoots the particles into the cells with the hope that at least one of the metal particles will just by chance happen to land inside the nucleus of a cell. like literally this is called ‘biolistics’. like ‘ballistics’ but it makes no fucking sense. 

here’s an analogy: your friend is trapped in a manhole on a construction site. instead of lowering down a bucket of supplies to help them like a normal person, you just tape the new rung to the front of a gun and just fucking shoot at the old rung. ‘dude!’ cries ur friend, ‘dude, what the fuck man!’. you do not listen bc u do not care. this may not sound like it would properly insert the rung like, at all, and a lot of the time it doesn’t, but sometimes it does. more often it just makes ur friend upset and sometimes injures them. it’s a very ‘then perish’ approach to gene editing, but that’s literally how we did it before we had the magic that is CRISPR. if you would like to try this yourself, there are multiple videos on youtube that apparently instruct you on how to build your own, just like the Dupont Pioneer corn scientists that originally jerryrigged the very first one in a corn breeding center lab in the mid 80s! wow! 

here’s a video of one firing. its a lot less climatic then i expected it to be (i’ve never seen one fired before in person); after a minute of the pressure building, the scientist flips a switch, and we see one of the protective coverings in the chamber just fucking break under the air pressure. i have no idea if its supposed to do that or not, but regardless i think its very symbolic of gene guns in general lmao. according to the description on the video, this is a test fire of tungsten particles coated with the DNA to make the successfully transformed cells glow. they’re firing at onion cells, which are commonly used in these test fires because they’re huge and make for bigger targets. they also note that if they’re lucky, about 1% of cells will end up actually glowing like they hope they will. thank god we have CRISPR now or we would never get anything done