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jigujellee · 2 years

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THROUGH WITH YU -> karina yu hates your guts and you don't really know why. | read part 2 here!

karina x reader angst word count: 3.8k warnings: there might be a swear word or two, nothing crazy

a/n: wow, another fic in less than 2 weeks? who is she? lol i'm jk but the first part to the karina enemies to lovers college au is here! there's only two parts, so hopefully, i should be able to get it out soon. don't worry, i'm also working on the requests you've all sent me so please look out for those. take care everyone, thanks for reading!

smu was home to numerous intelligent and hard working students who were slowly losing their sanity every day in order to achieve their future. if they weren’t burying their faces in their laptops or textbooks, students were drowning themselves in caffeine as they desperately try to work through the hell known as university. it’s definitely not easy for most, but then there are people like karina who make the university life look so easy.

karina yu graduated from kwangya high as valedictorian and received a full grant scholarship at smu where she is now a biomedical student with a dream to pursue a career in medicine. she also manages to maintain the top spot in the entire school while being the captain of the swim team and balances a part time job. the girl’s credentials are unmatched, you’d think she doesn’t have a social life but no. everybody and their grandmothers know exactly who karina is, and with a god given face, brain, and talent like hers, who wouldn’t be drawn to her? dubbed as the campus goddess, she captures the hearts of anyone who glances her way. karina could care less about the title though. she was nice to everyone she encountered and remained humble despite being treated like royalty at school. so when everyone’s attention is focused on something else, or rather someone else, karina suddenly becomes intrigued.

“alright class, that wraps it up for today. don’t forget, your assignments on DNA mutagenesis are due next Friday so i hope most of you have at least started on it”

as soon as the campus goddess finished typing up her last few notes, she sets a quick reminder for herself to finish the references for the assignment. karina’s work ethic was something every student dreamed to have in a perfect world, hence why it isn’t uncommon for students to ask her for help every now and then. her best friend ningning is a perfect example of these said students.

“so you’re going to help me with my assignment, right?” the blonde says, not even sparing a glance to karina as her eyes remained glued on her phone.

“ning, why do you still have to ask? i’ve been helping you with your assignments since we were in high school. but let me remind you that you’re smart enough to do it on your own. maybe if you spent less time on your phone, you would’ve gotten it done early”

“thanks for the ted talk but you know i gotta stay updated with the tea around here”

“right, so what’s new gossip girl hm?”

“well, jeno recently got injured after their last basketball game so he’s sitting out for the next few. then there’s yeji and ryujin who got into a pretty nasty fight and people are saying they still haven’t talked it out”

“isn’t it gonna be their 3 year anniversary in a few weeks? i hope they resolve things soon”

“well well well, would you look at that? seems like someone is fairly updated too” ningning chuckles and finally tears her eyes away from the phone to find karina putting her stuff away into a tote bag.

“you live and breathe tea and drama, and unfortunately, i’m the only one who has to hear all of it since i’m pretty much the only friend you have,” karina jokes.

“you make me laugh miss yu,” her best friend says dryly as rolls her eyes and continues to scroll through her phone once more. “oh, and there’s a new student coming in today. apparently they’re coming all the way from canada,” ningning turns off her phone and grabs her bag before sticking her arm out so that karina could link arms with her. the latter didn’t care much about the new transferee, not with her empty stomach practically ringing in her ears.

“yeah yeah whatever, let’s go grab lunch. i’m starving” she links her arms with ningning and the two make their way to the campus cafeteria.

they were greeted with crowds of students, which wasn’t a new sight to the two. almost all of campus knew karina ate in the cafeteria during lunch so they would always have an audience as they ate in peace. what was surprising to karina was that the students weren’t swooning over her like they usually do. instead, they were running right past her and making their way to the table where karina and ningning usually sat. confused, karina looks over at her best friend.

“why is everyone rushing to get over there? we’re not even there yet”

“you think i would know? i was beside you this entire time. but it looks like someone is sitting there already, i can’t see who it is though”

a girl in front of the two overhears their conversation before realizing who it was and immediately moves out of the way to let them pass. everyone else followed suit and the two manage to get a clear view of who was causing such a big crowd. they walk towards the table, but even as they get closer, they are unable to put a name to the face sitting in their usual spot.

as soon as they approached the unfamiliar person, ningning doesn’t hesitate to speak, “hi! i’m ningning and this is my friend karina!” the purple haired girl’s eyes widened at her friend’s sudden introduction, but not wanting to be rude, she just smiled and gave a small wave.

“hello! i’m y/n, it’s nice to meet you both” you say with a big smile plastered on your face.

“ah! you’re the new student, right? from canada?” you eagerly nod your head and continue to answer ningning’s never ending questions about your home country. meanwhile, the girl beside her stayed silent and just stared at you. you couldn’t tell what she was feeling, her face remaining stoic the entire time you were talking with her friend. you open your mouth to address her and try to include her in the conversation, but another student calls your name and invites you to eat lunch with them.

“karina and ningning usually sit here, so just sit with us for lunch” the student then whispered in your ear. you look back at the two girls and realize that they’ve been standing this entire time, so you immediately get up and allow them to sit at their respective table.

“well i’d be glad to answer your questions about canada some other time ning,” you chuckle. “i hope to see you both around more! sorry about taking your seat,” you say as your gaze lands on karina, who just quickly bows her head out of respect before taking a seat at the spot you were just in. ningning quickly hands you her phone for you to put your number in before letting you go. as you leave, you turn to take a look at the purple haired girl one more time.

you now understood why she was called the campus goddess.

funnily enough, the campus goddess wanted nothing to do with greek gods and goddesses, or any greek mythology in general. she hated history classes. the only reason she was taking it is because she needed an elective that wasn’t related to her major, so she chose ancient greek mythology and apparently, it was a really easy course. but even if this course was super easy, she got bored so easily. it was the only class that she rarely paid attention in and it made her want to fall asleep.

it doesn’t help that this class was a dreaded 3 hours of her professor going on and on about information that had nothing to do with what karina wanted to do with the rest of her life. oftentimes, her thoughts loved to wander off during class, and to her surprise, you are the one currently taking up space in her mind. karina couldn’t help but think about your smile, your dark brown eyes, your soft voice, the way your hair sat perfectly against-

“miss yu?” karina shakes her head and brings herself back to reality. was i really just thinking of the new student just now?

“sorry sir, what were you saying?”

“i asked which two groups fought during the battle of cynoscephalae?”

karina couldn’t bring herself to answer. she should know this, she did her readings on it so why couldn’t she remember? oh right, because some new girl was distracting her, that’s why.

“it was fought between the romans and the antigonids,” you spoke up after minutes of silence from karina. she looked back in shock, finding you three rows behind her. great, the person who’s been wrecking my train of thought is also in the same class as me.

you shoot her a wink with a smile, causing karina to immediately turn back around to the front, hoping you wouldn’t see her cheeks heating up out of embarrassment.

“that’s correct y/n, thank you. pay more attention karina, this isn’t like you”

“yes sir, it won’t happen again” karina sinks into her seat and groans internally for letting herself get distracted and embarrassing herself in front of you… and the class.

and now, she despised you for making her feel this way and decided that she wanted nothing to do with you.

so any attempt you made in trying to be her friend, whether it be buying her snacks, coffee, cup noodles, and even a whole cake, or trying to follow her on instagram and her other socials, karina shut all of it down. she couldn’t afford to be embarrassed like that anymore and she tried her best to avoid you, but she quickly learned that you were stubborn and you weren’t going to stop until you two were at least acquaintances.

“hi karina! i grabbed you a triangle kimbap and a choco pie in case you were hungry,” you hold out the snacks in front of her, hoping she’ll actually take them this time. but as usual, she just stares at them and her hands remain still by her side.

her eyes shift from your hands to your own eyes, and you could feel a bitter coldness being emitted from her dark brown orbs. “i’m going to make this very clear, y/n. i do not care who you are or where you came from, but i do not need you around me. buying me snacks is not going to get me to be friends with you, so drop the act. we are never going to be friends,” she says, words hitting you like a knife. your hands that are filled with snacks drop to your side as you watch the campus goddess walk away from you. from that moment on, you do your best to avoid her, hoping that you are finally giving her something she actually wants.

it’s only 9 in the morning, and karina is already having a horrible day.

“what? what do you mean i’m failing? that’s nearly impossible-”

“calm down karina, you’re not behind by much. with a little tutoring and some catch up assignments, you’ll be able to bring your grade up in no time,” her english professor says.

karina huffs in frustration. how could this happen? she swore she handed in all her essays on time and they were all done very well, so she had no idea how could she be failing the class.

“i asked the student who will tutor you to come in today so that i could introduce you two,” and as if on cue, there was a knock on the door.

“perfect timing. come in!”

karina doesn’t bother turning around to see who it was, still trying to rack her brain over how she could possibly be doing badly in english class.

“you wanted to see me professor lee?”

the purple haired girl’s eyes widened and her mouth falls slightly agape. she didn’t need to look at who it was; the voice said it all.

“thank you for coming, y/n! i wanted to introduce you to karina, have you met before?”

“yes, we share a few classes together” you say dryly.

you were aware that you had to tutor someone, but you didn’t know it’d be her. from where you were standing, you could see that she didn’t want to be in this setup either. she was avoiding your presence, putting all her attention onto the stack of papers on the professor’s desk and studying it as if it were the most intriguing thing in the world right now.

“with all due respect professor lee, i’m sure there are a number of other students who would be willing to help karina out. not to mention countless other students who speak english at a much higher level than i do, such as aeri, chaeyoung, jennie, yunjin, jisu, seungkwan.. need i list more?”

for the first time since entering the office, karina looks at you with a confused expression; she didn’t expect you to turn the opportunity down, not after all the nice things you’ve done for her just to be her friend. your focus remains on the professor as you wait for a reply, ignoring the other girl beside you who was trying to figure you out, the stack of papers on the desk now long forgotten.

“nonsense y/n, what better way to learn english than from someone who’s just transferred from canada? besides, english is your first language, correct?” you nod your head, unable to lie because the records were right there in front of the prof.

“then it’s settled! think of it as a way to get closer to one another. karina, i promise you won’t regret this and your grade will improve in no time! you two are dismissed, i’ll see you both on wednesday”

both of you bow your heads, and karina is the first one to get up and leave. you follow suit, rolling your eyes once you’re at the door because she didn’t even have the courtesy to hold it open for you. once you’re both outside of professor lee’s office, you’re about to retreat to your own dorm but karina stops you.

“hey”

you say nothing and just turn to look at her, waiting for her to continue what she wanted to say.

“2pm tomorrow at the library. don’t be late,” she says sternly.

with no ounce of emotion on your face, you turn around and leave the purple haired girl standing in front of the prof’s office.

you hoped this tutoring session will go somewhat smoothly.

no, it’s not going smoothly.

karina was the one who said not to be late, yet she’s the one who came almost 20 minutes late. she blamed it on ningning for asking her to accompany her while she talks to one of their other professors.

and now, karina hasn’t spoken a word to you since she got here. she didn’t bother asking for any clarification or any questions and just began working on her assignment, but you couldn’t care less. if she didn’t want to fix her grade, then so be it. you allowed yourself to enjoy this quiet time by catching up on your favourite book, but unfortunately, it doesn’t last long.

“here, check this for me”

you scan the paragraph writing assignment she had to do. with a pencil, you lightly circled her mistakes and even wrote down some comments on things that could be improved. when you hand it back to her, you watch as her eyes scan over the paper and she huffs in frustration. you continue to watch the campus goddess scribble onto her paper, erasing and rewriting things every other second. your eyes move to the paper and you notice her making the same mistake again.

“you did the same thing aga-”

“shut up, i got it” but even after she erases it, she does it again. this time, she realizes what she wrote.

“not a word, y/n”

“rina look, i just-”

“first of all, do not call me that. we’re not close, okay? and second, i don’t care that you were asked to help me. i just need to pass english and then i’m through with you,” without missing a beat, she continues writing her assignment.

you won’t lie, it hurt whenever karina dismissed you like that. you don’t even understand why she hated you so much. was it because you answered for her in class? or was it because you stole her seat on the first day? whatever it was, it still hurt. but if she was going to be like this towards you, then you figured you should be the same back.

and that’s how the rest of your tutoring sessions go. you both arrive at the library, not uttering a single word to each other. you immerse yourself in your book or in other school work, and you only say something if karina asks you. as you meet up more and more, however, you notice karina is slowly starting to ask more questions and actually initiate conversation but you always gave her a dry reply, not even bothering to look up at her as you answer. why should you? you were just here to help her.

after one of your tutoring sessions, you were walking back to your dorm when you suddenly receive a phone call. the caller ID was enough to make you decline the call, but you answer it anyway. you don’t bother saying hello, and just wait for the other party to say something.

“not even a hello? wow, who do you think you are?”

“what do you want?”

“jeez, what’s gotten into you? i just called to check up on you”

“i never asked you to check on me”

“god, you’re unbelievable. you should be thankful i’m even checking up on you even after what you did to your-”

“stop trying to act like my mother. you are not her and you will never be her, so just shut up and leave me alone,” you angrily say as you hang up, not letting her get a response in. you shove your phone back into your pocket and stormed off to your dorm, but you don’t notice the girl behind you who heard everything.

she didn’t mean to eavesdrop. if anything, she blames you for stopping in the middle of the hallway and answering the call, and even putting it on speaker phone. but she heard it either way, whether she wanted to or not. karina watched as you stomped away and she felt a heavy feeling in her chest - it was guilt. she’s been rude to you all this time when all you wanted was to be her friend. you even agreed to tutor her (though it was pretty much forced) and she was still acting like such a bitch to you. but after hearing the conversation, she couldn’t help but feel sad. she didn’t have the best relationship with her mom either, so in a way, she kind of related to you. she starts thinking that maybe you weren’t so bad after all.

a few more tutoring sessions and three assignments later, karina manages to get her grade back up. once she hears the good news from professor lee, she immediately goes to find you.

“y/n!”

you turn around to find an ecstatic and smiley purple haired goddess coming your way. she crashes into you and wraps her arms around you, but you just stand there and look straight ahead, leaving your arms glued to your side.

she finally lets go of you after what seemed like minutes of hugging, and she shoves a paper in front of your face.

“look! i got my grade back up, and it’s all thanks to you!”

“good. now we can go our separate ways,” you try to walk pass her, but she grabs your arm to stop you.

“wait! let me treat you to something to eat! as a thank you for helping me”

“i’ll pass,” and you try to walk by her again. she doesn’t stop you this time, but she starts following you instead.

“how about tomorrow? or next week? i’m free whenever, just let me kn-”

“what’s your deal, hm? why are you so nice to me all of a sudden? just because you got your grade up or what?”

karina’s smile fades and a nervous expression appears on her face, scared to tell you why she was acting this way. she fidgets with the paper in her hand, avoiding your gaze and biting her bottom lip.

“so what do you want?” you ask, trying to get an answer out of her.

“i..” she starts. “i overheard your phone call with your mom. i didn’t mean to, it’s just you were right there and you even put it on speaker phone so i just happened to hear everything..” you say nothing, and you wait for her to continue.

“i feel bad for how i’ve treated you all this time. the truth is, i get it. i know what you’re going through, and it’s okay to-”

“stop,” karina looks at you, and she looks scared but she’s not scared that you were angry, she knew you’re probably pissed at her. what was scaring her is the lack of emotion you were showing. she wanted you to scream at her, to cuss her out for being such a bitch, but instead you’re as calm as ever and it terrifies her to her core.

“she’s not my mother. that was my stepmom who tries way too hard to be my mother,” you say calmly. you start making your way to her, making sure that she hears what you have to say next loud and clear. once you're right in front of her, you continue.

“don’t act like you fucking know me just after hearing one phone call. if you’re being nice to me because you feel bad for me, then just save it. i don’t need your pity and i don’t need you around, got it? i’m through with you” you’re close enough to feel her breath on your lips, but you back away as soon as you’re done talking to her and you leave her in the middle of the hall with people were staring, but you didn’t care. you didn’t need karina or her pity, and the campus goddess got that message loud and clear. but it still hurt her. it hurt enough to make tears fall from her eyes, and karina rarely ever cries. she wipes away whatever tears were on her cheek and starts making her way to meet with ningning.

karina didn't want you to be through with her, but she deserved it. especially since she's the one who said it first.

#kpop scenarios #girl group scenarios #kpop imagines #gg scenarios #gg imagines #aespa #aespa karina #karina yu #yu jimin #karina angst #karina scenarios #karina imagines

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materialsscienceandengineering · 5 months

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A tiny, hard-working bacterium -- which weighs one-trillionth of a gram -- may soon have a large influence on processing rare earth elements in an eco-friendly way. In a new study, Cornell University scientists show that genetically engineering this bacterium could improve the efficiency for the purification of elements found in smartphones, computers, electric cars and wind turbines, and could even boost global economic supply chains. Vibrio natriegens, the bacterium, offers a sustainable method -- called biosorption -- to extract valuable and needed elements rather than use older, polluting solvent-heavy methods. The Cornell research, "Multiple Rounds of In Vivo Random Mutagenesis and Selection in Vibrio Natriegens Result in Substantial Increases in REE Binding Capacity," was published Dec. 6 in Synthetic Biology, an American Chemical Society journal.

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gaygayaurel · 8 months

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As game Lambert #1 fan 5ever the Nerflix Lambert sucks but not bcs of what people think? (I didnt read book of elves I love and respect myself sometimes )

As in game Lambert is kinda fun in that he got actually defined compared to Novels and Hexer where he did not exist ad character proper. He is deeply mean and sarcasric person, being willing to chew out his closest friends and enemies alike. He isnt as morally concerned abt stuff as geralt and when someone asks him to kill a monster he'd do it. Fuck he'd even go as far as use Axii to make two bandits die in horrific way. This is after all his lot in his shitty miserable life. He hates witchery and witchers and the very concept of this much suffering ("But you kept the table" he says furious to Vesemir as they stand above screaming Uma). His attitude is just such a complete 360° from Geralt' silent acceptance of what was done to them. It truly becomes the only voice of like hey fuck what happened to us, fuck it all to hell. Hes an utter fucking dickhead and hell provoke people for no reason (talkinf abt geralt and triss in front of phillipa for no reason) (i deadass dont think he would fuck up yens stuff on purpose tho #;#&#&)

His main core personal element is revenge. In his short appearence in w1 he proclaims desire to slaughter salamandra for killing Leo. In W3 he goes on massive revenge rampage spanning CONTINENTS for a guy we dont know (and thats pretty cool to me, implying he has adventures outside geralt, both him and eskel). He says his first action after he left Kaer Morhen was to find and kill his dad ( and him being sad he couldnt save his mother his life is all just empty revenges that will never fill the holes of people hell miss).

But also main Core element of Lambert is also love as cheesy as it sounds. He cared deeply for Leo and Aiden and even his own mom. After Triss. Got conked out by a mage guy in witcher 1 he cared for her and watched over her (they were hardcore inplying shipping which is funnt but whatever). He literally puts his life on line dor Ciri and Geralt. The thing is he is dickhead but he will do Everythinf for those few peoples he has left in his life.

The Point is games being games and larger allowed Lambert to have depth and nuance. He is imo one of the most interesting and coolest game characters. Netflix Lambert however did not have the time for variety of reasons to get that.

One is Lambert is very minor person in books. Second is that the show didnt...realy care abt witchers past vesemir maybe. So he wasnt a focus. In the end what we get is disappoitninf character not helped by the fact most witchers in netflix are cannon fodders for baba yaga.

ONE issue that I have is people saying Lambert was a dick to Ciri and thats OOC. While I cant speak from the POV of books (altho my friend who did read them say he is sexist), from POV of game thats untrue. In fact I believe game Lambert would VERY much be a fucking dick to Ciri fron a start. It doesnt even need to have sexist colouring to it. This dude HATES witchering. He hates the mutagenesis and the pain of it all, the destiny in it. I firmly believe he wouldnt be OK with a bew trainee and guess what? While he didnt live through instructors not giving fucks abt new witchers because like 1/20 live to become witchers he LIVED through it. On his skin. I firmly believe Lambert being DICKHEAD to ciri at first is nit only a whiff of the complex game!Lambert but a decent start of its own standalone character.

In witcher 1 also wheb tou tell him Leo died he laments he "was not ready". Leo. Just like ciri never got his mutagens (take this with grain of salt because leos whole character is weird tm). So him being an miserable instructor who will push you until you cry is in character ingame. This guys has ten layers of issue.

What Netflix misses is the fact we dont SEE lambert getting to his relationship Ciri where we see rhem albeit briefly in game (willing to fight to death for her). We just have this awkward jump from utter hostility to them beinf kinda pals after baba yaga fight. In the end netflix lambert is just. Boring.

Also hes not a balding fuck and i cant forgive that

#Lambert witcher #The witcher #I lov witcher 3 lambert so much hes my legit fave sbsbs #I love that I can only enjoy loyal mean gays who bullied a kid once #there was actually dickhead fellow trainee of geralt in hexer who i suspected of being like base for lambert characterization in the games #because the games were v much made in context of hexer

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fungh0u1 · 23 days

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playing and having fun in ms paint

#mutagenesis drive #oc: marnie #oc: joan #ahh i dont think this is necessarily a good drawing of them. but i do love ms paint i havent used it much. but i should #mainly drew this because i got a shirt like the one i drew joan (right) in. yayy ^_^#my art

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didanawisgi · 5 months

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Abstract

Therapeutic applications of synthetic mRNA were proposed more than 30 years ago, and are currently the basis of one of the vaccine platforms used at a massive scale as part of the public health strategy to get COVID-19 under control. To date, there are no published studies on the biodistribution, cellular uptake, endosomal escape, translation rates, functional half-life and inactivation kinetics of synthetic mRNA, rates and duration of vaccine-induced antigen expression in different cell types. Furthermore, despite the assumption that there is no possibility of genomic integration of therapeutic synthetic mRNA, only one recent study has examined interactions between vaccine mRNA and the genome of transfected cells, and reported that an endogenous retrotransposon, LINE-1 is unsilenced following mRNA entry to the cell, leading to reverse transcription of full length vaccine mRNA sequences, and nuclear entry. This finding should be a major safety concern, given the possibility of synthetic mRNA-driven epigenetic and genomic modifications arising. We propose that in susceptible individuals, cytosolic clearance of nucleotide modified synthetic (nms-mRNAs) is impeded. Sustained presence of nms-mRNA in the cytoplasm deregulates and activates endogenous transposable elements (TEs), causing some of the mRNA copies to be reverse transcribed. The cytosolic accumulation of the nms-mRNA and the reverse transcribed cDNA molecules activates RNA and DNA sensory pathways. Their concurrent activation initiates a synchronized innate response against non-self nucleic acids, prompting type-I interferon and pro-inflammatory cytokine production which, if unregulated, leads to autoinflammatory and autoimmune conditions, while activated TEs increase the risk of insertional mutagenesis of the reverse transcribed molecules, which can disrupt coding regions, enhance the risk of mutations in tumour suppressor genes, and lead to sustained DNA damage. Susceptible individuals would then expectedly have an increased risk of DNA damage, chronic autoinflammation, autoimmunity and cancer. In light of the current mass administration of nms-mRNA vaccines, it is essential and urgent to fully understand the intracellular cascades initiated by cellular uptake of synthetic mRNA and the consequences of these molecular events.

#covid-19 vaccine #covid-19 #print this off later #LINE-1 #mrna vaccine #fav #important

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science-sculpt · 1 month

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Amplifying Revolution: The Polymerase Chain Reaction (PCR)

Imagine a scenario where you have a crucial document, but there's only one fragile copy. You need numerous duplicates to analyze and share. This is exactly the challenge faced by scientists dealing with DNA. Thankfully, a revolutionary technique called Polymerase Chain Reaction (PCR) comes to the rescue. PCR, often referred to as molecular photocopying, is a fundamental tool in molecular biology. It allows scientists to exponentially amplify a specific DNA segment, creating millions of copies from a minuscule sample. This has revolutionized various fields, from diagnosing diseases to unraveling genetic mysteries.

The credit for inventing PCR is widely attributed to Kary Mullis, a biochemist working at Cetus Corporation in the early 1980s. Inspired by his nighttime drives through California, Mullis envisioned a method for exponentially copying DNA segments through repeated cycles of heating, annealing (primer attachment), and extension (polymerase-mediated DNA synthesis). This elegant concept became the foundation of PCR. Mullis's concept was brilliant, but a crucial hurdle remained. The process required a DNA polymerase enzyme that could withstand repeated heating and cooling cycles. The solution came from an unexpected source: hot springs. In 1976, researchers discovered Taq polymerase, a heat-stable enzyme isolated from the thermophilic bacterium Thermus aquaticus. This discovery was a game-changer, as Taq polymerase could function optimally during the high-temperature steps of PCR. In recognition of its transformative impact on science, Kary Mullis was awarded the Nobel Prize in Chemistry in 1993, alongside Michael Smith, who pioneered site-directed mutagenesis.

While the core concept of PCR was established, the technique required further refinement. Pioneering researchers like Henry Erlich at Cetus played a vital role in optimizing reaction conditions, automating the process, and developing the now-ubiquitous thermal cyclers that precisely control the temperature changes needed for PCR. The 1980s and 1990s witnessed a surge in PCR applications. In 1985, PCR was used for the first time to analyze sickle cell anemia, demonstrating its potential for clinical diagnostics. Forensic science embraced PCR in 1987, with the successful amplification of DNA from a single human hair. By 1989, highly sensitive DNA fingerprinting techniques based on PCR became a game-changer in criminal investigations.

At the heart of PCR lies a clever exploitation of the natural process of DNA replication. The key players in this drama are:

Template DNA: The DNA sequence that contains the target region to be amplified

Primers: Short sequences of nucleotides that flank the target DNA region and serve as starting points for DNA synthesis.

DNA Polymerase: Enzyme responsible for synthesizing new DNA strands by extending the primers using nucleotides.

Nucleotides: The building blocks of DNA, including adenine (A), thymine (T), cytosine (C), and guanine (G).

Buffer Solution: Provides optimal conditions for the enzymatic reactions to occur.

Thermal Cycler: Instrumentation used to automate the PCR process by cycling through different temperatures.

At its core, PCR mimics the natural process of DNA replication within an organism. However, PCR condenses this complex process into a series of controlled steps carried out within a test tube. Here's a breakdown of the PCR cycle:

Denaturation: The first step involves heating the reaction mixture to a high temperature (usually around 95°C), causing the double-stranded DNA to separate into two single strands. This process is known as denaturation.

Annealing: The temperature is then lowered to allow the primers to bind (anneal) to their complementary sequences on the single-stranded DNA. This typically occurs around 50-65°C, depending on the primer sequences.

Extension: With the primers bound, the temperature is raised again, and DNA polymerase synthesizes new DNA strands by extending from the primers using the nucleotides present in the reaction mixture. This step occurs at a temperature optimal for the DNA polymerase enzyme, typically around 72°C.

Cycle Repetition: These three steps—denaturation, annealing, and extension—are repeated multiple times (usually 20-40 cycles), resulting in an exponential increase in the number of DNA copies. Each cycle doubles the amount of DNA, leading to millions of copies of the target sequence after just a few cycles.

The beauty of PCR lies in its repetitive nature. With each cycle, the number of copies of the target DNA segment doubles. After 30 cycles, for example, you can have billions of copies of the specific DNA region, enough for further analysis.

This versatile technique has spawned numerous variations, each tailored for a specific purpose. Let's delve into some of the most common types of PCR:

Real-Time PCR (qPCR): Real-Time PCR, or quantitative PCR (qPCR), revolutionized nucleic acid quantification by enabling the real-time monitoring of DNA amplification. This technique utilizes fluorescent reporter molecules to measure the accumulation of PCR products during each cycle. qPCR is invaluable in gene expression analysis, microbial quantification, and diagnostic assays due to its high sensitivity and quantitative capabilities.

Reverse Transcription PCR (RT-PCR): Reverse Transcription PCR combines PCR with reverse transcription to amplify RNA sequences. This technique converts RNA into complementary DNA (cDNA) using reverse transcriptase enzyme before proceeding with PCR amplification. RT-PCR is pivotal in gene expression studies, viral load quantification, and the detection of RNA viruses such as HIV and SARS-CoV-2.

Nested PCR: Nested PCR involves two rounds of amplification, with the second round using a set of nested primers that bind within the product of the first round. This nested approach increases specificity and reduces nonspecific amplification, making it ideal for detecting low-abundance targets and minimizing contamination. Nested PCR is commonly used in forensic analysis, pathogen detection, and rare allele identification.

Multiplex PCR: Multiplex PCR allows simultaneous amplification of multiple target sequences within a single reaction. This technique employs multiple primer sets, each specific to a distinct target region, enabling the detection of multiple targets in a single assay. Multiplex PCR is valuable in microbial typing, genetic screening, and detection of pathogens with complex genetic profiles.

Digital PCR (dPCR): Digital PCR partitions the PCR reaction into thousands of individual micro-reactions, each containing a single DNA template molecule or none at all. By counting the number of positive and negative partitions, dPCR accurately quantifies target DNA molecules without the need for standard curves or reference samples. This technique is useful for absolute quantification of rare targets, allelic discrimination, and copy number variation analysis.

Allele-Specific PCR: Allele-Specific PCR selectively amplifies alleles containing specific nucleotide variations, enabling the detection of single nucleotide polymorphisms (SNPs) or mutations. This technique utilizes primers designed to match the target sequence with single-base mismatches at their 3' end, allowing discrimination between different alleles. Allele-Specific PCR finds applications in genetic testing, pharmacogenomics, and population studies.

PCR's ability to amplify DNA has made it an indispensable tool in various fields. Here are a few examples of its diverse applications:

Disease Diagnosis and Surveillance: PCR plays a pivotal role in the rapid and accurate diagnosis of infectious diseases. By amplifying specific nucleic acid sequences, PCR enables the detection of pathogens with high sensitivity and specificity. PCR-based tests have become indispensable in diagnosing viral infections such as HIV, hepatitis, influenza, and COVID-19. Additionally, PCR facilitates the surveillance of disease outbreaks and the monitoring of antimicrobial resistance.

Genetic Testing and Personalized Medicine: PCR empowers genetic testing by enabling the detection of genetic mutations, polymorphisms, and variations associated with inherited diseases, cancer, and pharmacogenomics. Through techniques like allele-specific PCR and real-time PCR, researchers can identify disease-causing mutations, assess drug efficacy, and tailor treatments to individual patients. PCR-based genetic tests have transformed healthcare by enabling early disease detection, risk assessment, and personalized therapeutic interventions.

Forensic Analysis and DNA Profiling: PCR has revolutionized forensic science by enabling the analysis of minute DNA samples collected from crime scenes. Techniques like short tandem repeat (STR) analysis and multiplex PCR allow forensic experts to generate DNA profiles with high resolution and accuracy. PCR-based DNA profiling is used in criminal investigations, paternity testing, disaster victim identification, and wildlife forensics, contributing to the administration of justice and conservation efforts worldwide.

Environmental Monitoring and Microbial Ecology: PCR facilitates the study of microbial communities in diverse environments, including soil, water, air, and the human microbiome. Environmental DNA (eDNA) analysis using PCR-based methods enables the detection and characterization of microbial species, including bacteria, fungi, and archaea. PCR-based assays are employed in environmental monitoring, food safety testing, and microbial source tracking, aiding in the preservation of ecosystems and public health.

Agricultural Biotechnology and Food Safety: PCR plays a vital role in agricultural biotechnology by enabling the detection of genetically modified organisms (GMOs), plant pathogens, and foodborne pathogens. PCR-based assays are used to verify the authenticity and safety of food products, detect allergens, and monitor the presence of contaminants such as pesticides and toxins. PCR-based technologies contribute to ensuring food security, quality control, and regulatory compliance in the food industry.

Evolutionary Biology and Phylogenetics: PCR-based methods are indispensable tools for studying evolutionary relationships and biodiversity. Techniques like DNA barcoding and metagenomics employ PCR to amplify and analyze DNA sequences from diverse organisms, elucidating their evolutionary history and ecological interactions. PCR facilitates the identification of new species, the study of population genetics, and the conservation of endangered species, enriching our understanding of the natural world.

PCR's versatility and precision make it indispensable in unlocking the secrets of genetics and unraveling complex biological mysteries. Its ability to amplify minute DNA samples with remarkable speed and accuracy has opened doors to countless possibilities in research and diagnostics. s we delve deeper into the intricacies of the genetic world, PCR will undoubtedly remain a powerful tool for unlocking the secrets of life itself.

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