DNA Structure and Replication: Crash Course Biology #10

Hank introduces us to that wondrous molecule deoxyribonucleic acid - also known as DNA - and explains how it replicates itself in our cells.
References:
www.nature.com/nature/dna50/wa...
publications.nigms.nih.gov/the...
rst.gsfc.nasa.gov/Sect20/A12.html
www.nature.com/scitable/topicp...
www.uic.edu/classes/phys/phys4...
www.buzzle.com/articles/dna-re...
www.dnareplication.info/stepso...
salamandercandy.wordpress.com/...
www.sdsc.edu/ScienceWomen/fran...
www.fmi.ch/members/marilyn.vac...
www.strangescience.net/rfrankl...
1:41 link to Biological Molecules • Biological Molecules -...
Table of Contents:
1) Nucleic Acids 1:30
2) DNA
-A) Polymers 1:53
-B) Three Ingredients 2:12
-C) Base Pairs 3:45
-D) Base Sequences 4:13
3) Pop Quiz 5:07
4) RNA 5:36
-A) Three Differences from DNA 5:43
5) Biolography 6:16
6) Replication 8:49
-A) Helicase and Unzipping 9:22
-B) Leading Strand 9:38
-C) DNA Polymerase 10:08
-D) RNA Primase 10:24
-E) Lagging Strand 10:46
-F) Okazaki Fragments 11:07
-F) DNA Ligase 11:47
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[@pedrosmith4529]

My earphones get tangled all the time, but miles and miles of DNA don't. Mind blowing.

[@vjlove1218]

Stan Lem yes! But DNA has a LOT of help from many different proteins

[@its_tomothy]

For some reason, I read that as "My earlobes get tangled all the time" :0

[@lalaithan]

@@its_tomothy do your ears hang low? Do they wobble to and fro?

[@its_tomothy]

@@lalaithan yeah, im actually dobby the house elf lol

[@ddbrayen1aramai1tii]

Its actually tangled and become 3D coumpound

[@her1468]

11 years later, the video still better than a two hour lecture

[@mattalex543]

This dude is getting me through college one video at a time.

[@lilzod4862]

College?!? Bruh what kind of college you in?

[@zoefoster6750]

I was gonna say, I’m learning this in Level 2 biology here. (I’m 15, in a 16 year old class)

[@FishoeShoe_da_great]

"why is a teenage boy similar to helicase? they both want to unzip your genes (grins)" I'm speechless

[@rheasharma2939]

Hank: "Hey you wanna make one?" Me: I'm 12

[@tankgunner32]

its crazy how a youtube channel that i get for free is a better teacher than the teacher i paid hundreds of dollars for. goddamn the college life.

[@ebkdoa3535]

Tell that to the people who will be paying money to watch this in a couple months

[@mycaroxas4088]

Paid with ads my friend. and yet, I love Crash Course!!!!

[@BannerOfBlasfemy]

college should be free

[@bluon259]

BannerOfBlasfemy college is free for me at least, all I had to do was write a paper and take a test. (I’m a freshman in high school). It all depends on where you live and where you look, and whether or not the opportunity is there yet. But yeah, people should go to college for free if they have the drive for it.

[@sourcetext]

College is a for profit business. The ancient Greeks called them Sophists

[@ExplaurenwithLauren]

Good Luck on your test/exam/final/quiz tommorow that we both know you are just now studying for... éxpöšêď ;)

[@georgiaalexandriaa]

it's actually today

[@kyleharvey3824]

100 percent facts

[@EarlyOwOwl]

Thanks fren

[@hxhchimeraantarc2268]

Exposed

[@jays9572]

i feel very ,much attacked

[@JulioFromBoston]

Editing team: "Hank please hold up a shoelace and be amazed by it"

[@rishinixon7560]

ha!

[@katiesingsthings6453]

Anyone else cramming the day before the exam?

[@mariadedios9081]

+KatieSings&Things ME!

[@catherinec3735]

+KatieSings&Things I'm glad im not alone XD

[@arwahasnain5624]

This is the time Crash Course's views exponentially increase the most

[@darkdestiny3700]

maybe...

[@shingaikagunda6426]

Meeeee!!!! Lol

[@YoyoBear12]

Thank you so much for covering Rosalind Franklin, some of my previous instructors only briefly mention her and they rarely discuss her major contributions to the discovery of the DNA structure.

[@christinemilling8568]

I started teaching biology in 1993 and I KNOW my kids (now middle aged) KNOW it was Rosalind Franklin who did the work. Hank, thank you. I left teaching, but am thinking about getting back into the classroom. Using your videos to study up for the test to get recertified. :)

[@toshido_yamada]

Gl, i hope you get re certified

[@purplegypsylady777]

Please.. The world needs good teachers!!

[@keshiaduplooy119]

The funny part about biology is that everyone pronounces everything differently

[@surajbhat5447]

this 12 minute video basically goes over eveything we've learnt in pre-ap bio's dna unit, which took 2 weeks for us. Thank you Hank

[@Epicgamerbro2000]

He explained t better than my lazy ass teaxher

[@Angelicmey]

+suraj bhat same

[@djmoneystacks3600]

+Dale are you mad😁😁😄

[@jeremytownsend6805]

+Dale Some teachers can't have class lectures and this is more interesting than reading a chapter in a textbook.

[@wizardvenom8500]

+Dale You can't even speak English lol

[@alannar.8701]

Trying not to fail my bio final. This is so helpful, and I want to thank the Green brothers for starting the channel, and the whole CC team for making it a reality. You guys are kind of the best.

[@yelectric1893]

Good luck

[@beckylieb2637]

awesome idea and dedication indeed... but they have some financing... bet they would be shut down if they taught some of the truth in science and history. ....

[@minjeekim3167]

When Hank said "POP QUIZ!" my heart started racing so fast.

[@riyasingh110]

HANK: Hey you wanna make one Subtitles says :oh dear god *Squeak**squeak*

[@cyberxxxcyberxxx9464]

I like the adult jokes on this episode😁😅

[@katieniwa7961]

I don't understand the joke...

[@PersimmonHurmo]

@@katieniwa7961 you're too young, get off the adult internet

[@TheHappyHummy]

His name is hank...

[@joestar8112]

Oh my oh my

[@mariakal605]

Usually when I watch videos to catch up on material idk the night before an exam I watch it in 1.5 speed but these crash course videos are the only ones I actually have to watch in like .5 speed omg

[@med8615]

working with 2x speed over here, gl.

[@jettlaxholly]

mariaarakal lol I’m usually at 1.25 speed with home because he already talks fast, but I have no time to waste

[@rachelelizabeth6017]

jett lax same! I always have mine at 1.25 or 1.5 speed! 😄😄😄

[@matthewvillalba-mutis6545]

When he said "Pop Quiz", my heart jumped. Sadly, I'm used to my science teacher saying that.

[@alicemeliksetian7981]

Matthew Villalba - Mutis thats what happened to me when he said “ *hey, you wanna make one* ”

[@Dixie.Normus0811]

Who’s here cramming before a test in 2019 lol

[@ryna2502]

y’all doing the AP test?

[@aarishhanif1837]

Yep

[@daciannabel9076]

Me😂

[@dearielbell663]

Me I have the biology staar tomorrow 😔😭

[@gomamon15]

Me right now for a final. Not that i wanted to cram but I have job and other classes, so here i am... tons of luck everyone

[@fredericavonsiemens6956]

anyone find it weird to think about how when this video was first released it probably got like 20,000 views but then over so many years millions of students watched it

[@missfluffybuns7759]

Kudos for giving Rosalind Franklin the credit she deserves!

[@laurasutherland2352]

Kinda bothered me that he didn't mention that women scientists tend to be disregarded for the sole fact of their being female. Still, love me some Hank Green.

[@pastsubstance2930]

It's pretty sad that that is a controversial topic to even discuss about.

[@victorfergn]

hmm the info is wrong, it wasn't Franklin who shared the info (she didn't like sharing anything, she even disliked when other people got into her lab) the one who shared the info was Wilkins, he showed the picture of the double helix to Watson; Franklin got furious about that (Wilkins and Franklin hated each other) Besides... she was far from theorizing how DNA worked, it was Watson how figured it out. Obviously Franklin had a key role but she wasn't Emmy Noether.

[@pastsubstance2930]

Just another Bird no not everyone. Probably the people you know and where you come from highlights Rosalind’s scientific feat but not every country.

[@seamusmcc5]

During the diagram from 3:00 to 3:40 all of the carbons that you circle and label are 5' carbons. The 3' carbon is the carbon that the phosphate group bonds to on the next nucleotide. So on the left stand the 3' carbon of the bottom sugar would be the very bottom left carbon with the two atoms (hydroxyl group) hanging off of it, and the corresponding carbon in each subsequent sugar.

[@laurenwallace8204]

I don't remember Crash Course being this complicated when I was in 9th grade biology, though I guess I should be thankful that 6 years later it is still helpful for my college level genetics class.

[@melaniec9079]

I love how the captions say "Hank why" when he told the helicase joke.

[@luigisim3]

"Hey... you wanna make one?" -Hank, 2012

[@sarah45532]

I laughed so hard xD

[@hi-lo1jm]

"(oh dear god)" -The subtitles, 2012

[@anjalimishra6470]

[when talking about teenage boys and helices both unzipping genes] Hank why- The subtitles

[@evyuwu4509]

PlatinumLuxray freaking creepy, we’re currently watching this is science class.

[@Kpoper4life]

"How is a teenage boy like the enzyme Helicase? They both want to unzip your genes" Oh boy...

[@ThingsUShouldLike]

My teacher showed this video in class and literally muted that part 😂😂😂 I got curious to what he said so I’m here now...

[@stefanli1755]

YEESSSSSS!!!!!

[@kikialeaki1850]

Oh helicase

[@monicavega-hernandez8787]

minute 3:07-3:42 has an error. The 5' is correctly highlighted but the 3 ' is wrongly highlighted.

[@ryankruskamp8973]

Thank you! It wasn't making sense so I checked the comments to make sure.

[@hifrax]

and i think the 10:57 part has an error as well. doesn't the lagging strand go in 5'-3' direction?

[@Jaspertt1]

@@hifrax yeah i think so as well. I think what they meant is that the lagging strand goes into the 5'-3' direction which would mean the DNA polymerase won't work 'efficienly' since it cannot go in the opposite 3'-5' direction

[@abdallab8511]

Yess i am checking the comments to make sure

[@gretchendean7346]

@@ryankruskamp8973 great that folks who caught that commented. Comments RULE!

[@xenaval]

my science teacher played this in class and when it got to the joke omg I'm screaming

[@JackT13]

Oh behalf of my dog who just watched this, he says he 'is most certainly not a human and did not care for the accusation'. I'm afraid he has unsubscribed

[@LuisSierra42]

My cat had a similar reaction

[@shyamalsingaravelu92]

tell your dog hes taken drugs to be able to even understand this

[@JackT13]

Shyamal Singaravelu he just said 'ketamine is a wonderful thing'

[@johnbradford6875]

I was put on ketamine after a had several surgeries within a month (they were worried about the amount of opioids I had been on, and the amount needed to control pain straight after surgery having a shoulder replacement might kill me post-op). I beseech the medico's out there, be it G.Ps, surgeon, nurses etc, to give patients the heads up about ketamine BEFORE the surgery - I came out of surgery, woke in the recovery room, and thought I was in a cartoon - everyone looked like something between a Disney character and Avataar (did I spell that right?). I would have panicked, except I was too smashed. I asked if I was hallucinating, and some guy I assume to be the anaesthetist said "no," that's the ketamine," - if this wasn't hallucinating, I need a new definition. I was in a lot of pain, but it was someone else's pain, if that makes sense (if you were on ketamine it might - it's called a "dissociative state", IMT). Very trippy. Wonder if animals have this happen?

[@JackT13]

+John Bradford you are a cartoon. Or at least your user icon suggests such

[@JKay5phD]

Good luck tomorrow everyone!

[@jennanicole6354]

JKay5phD exposed

[@AndrejNikolov-xw2gi]

Thanks man! :)

[@l3mi11ion]

JKay5phD thanks bro!

[@VikasYadav-to1xr]

Thanks:)

[@ainsley5563]

lmaooo

[@whiteeyedshadow8423]

"hey, you wanna make one?(oh dear god)" lol

[@jaredschnellbacher3204]

5:28 "See how that works? It's not super complicated" yEaH oKaY

[@coconutsharksinthewater4728]

same i didn't get it at all xD

[@alhassan5623]

I wish he is my anatomy teacher, I would get A so easily. my anatomy final is tomorrow and your videos help me in not wanting to read half a textbook

[@KitKatKool99]

SamE AND I SEE CHANYEOL

[@alhassan5623]

+Zsófi Szabó I passed my test yay!!! I can watch exo videos all now

[@humixmusic4lyf]

+pcy_exo2 congrats! ^u^

[@alhassan5623]

+humixmusic4lyf thank u!!^^

[@whenidieburymewithapenguin3136]

I see my bias in you profile pic :3 Congrats on passing btw X"D

[@MangaEater68]

Thank you for translating my textbook into understandable English terms. I love you

[@jaydenjiang2767]

I love Hank Green, his videos are so funny. I honestly don't care what he talking about, it is just sooooooooooo interesting.

[@batumanav]

I found myself in here when I feel hard to understand a subject in biology. Than, BOOM. It feels helixciting.

[@xxdavexx23]

I'm glad he included that Rosalind Franklin contributed to the findings of the DNA structure not until this year after my bio teacher told us about Rosalind Franklin have i found out that it wasn't all just Watson and Crick. I have lost lots of respect for Watson and Crick after that day.

[@Wolfeywolf16]

It angers me to see how discredited she was

[@ohkaryukai]

Taylor Clay they literally stole her work. you'd be surprised at how often men are credited for things women did. Ava Lovelace, Sanora Babb, Lise Meitner, Cecilia Payne, Hedy Lamarr, Vera Rubin. It's pretty awful.

[@nexusmares3371]

harumi Well let's not get carried away. "You'd be surprised at how often men are credited for things women did." Making statements like that perpetuate sexism. It's not like men everywhere have declared war on women and are out to steal their work. What if Watson and Crick had been women? It should stay a "x" stole from "y" issue, which is what it really is, not a man stole from woman issue.

[@ohkaryukai]

Ella Blun preach.

[@ohkaryukai]

Vinicius Fernades i suggest reading a few of her biographies if you'd like to learn more =) she was pretty rad in real life.

[@gregjang5402]

"Hey. You wanna make one?" I'm eleven.... My god....

[@arabeasy]

Lololololololololololollolololololoollolllloolol

[@TheSpicySimon]

"Hey, you wanna make one?" "Im a guy." "My god"

[@gregjang5402]

So am I.

[@rexyboi466]

So am i

[@gregjang5402]

School homework.

[@bbqyee7350]

Who is watching this before the AP Biology test? Mine is next Monday fml

[@ChiNguyen-mp5kd]

Haha me too but im happy with an 1 😂

[@carlie3628]

Same

[@anselcheesecake419]

@@carlie3628 same

[@giannagowe8486]

My cape Unit 1 is tomorrow

[@TheForgottenStory]

Yuh bug mine is first day of school

[@Sam-vs6rg]

0:45 turn on subtitles, will not disappoint you I swear

[@NoyumiAo]

Was having trouble remembering all the steps of the lagging strand but now remembering it for being a scumbag strand makes it so much easier

[@rafaelcontreras4358]

Jiji meAmeliacontreras

[@rafaelcontreras4358]

Creo ieuyfieyeutdy

[@oayabacnhoj6855]

I cried about how informational this is.

[@HomicideHeather]

For the first time in my two years in college, I actually understand what I am seeing. Thank you. I am in the MLT program trying to understand how PCR testing works but in order to do that I realized that I REALLY need to comprehend DNA and how it is made in order to understand how it is taken apart and analyzed. You have really given me a strong visual and I can't thank you enough.

[@yijieguo5908]

I remember watching this video for exams in middle school and high school. Now I'm in college, and I'm here once again :(

[@sidsin7538]

Crash Course is one of the best things to be on youtube, its fun to watch educational and overall helpful. You guys have proven that knowledge is power in so many ways, breaking down complex subjects while maintaining a high energy level teaching process which does not leave a student sleeping. You guys are like the Bill Nye of our time, keep up the good work. Its really pathetic that more people don't know about your work, grade schools should promote your program, but then again they are more focused on their sports teams, but overall for all of us non-athletic people you guys are champs.

[@ARedVelvetBunnie]

HOLD ON A SEC 'WANNA MAKE ONE'?????

[@theultimatedoom6896]

Make a DNA model xD

[@ARedVelvetBunnie]

lmao I got that in a wrong way

[@vanessanelson9330]

lol put on captions/subtitles "( oh dear god)"

[@mahdiyadegari8282]

Oh dear

[@kingbartholomewthe1above317]

about to type that

[@yililiang2067]

who has an incompetent teacher 🙋🏻‍♀️

[@blizzi8428]

OMG PLS DONT GET ME STARTED :((( I used to love biology class and was super good at it, then i got a new teacher and started not caring about anything, because he is that bad at teaching. It makes me depressed

[@lissetsantana3158]

🙋‍♀️ mi microbiology professor is the worst!

[@paigemc2107]

@Winnifred Ikpea We must be in the same class XD

[@paigemc2107]

You have no idea. XD

[@ClawedAsh]

My Bio teacher is horrible so here I am

[@skylerparadise2]

Hank. You are a blessing to every student in the world. Reading and digesting a convoluted and confusing textbook is so much easier after getting a grasp on the general idea first from watching these videos. Thank you so much!

[@marianascimento1498]

On 3:35 there's a mistake in the sketch. The 3' carbon is indicated on the 5' carbon, instead of the 3'

[@esmeraldacuriel4618]

+Maria Nascimento yes i was so confused about that

[@natattacc99]

So...which side is 5' and which side is 3'?

[@coenijn]

+NH.-B Well the 5'-prime end was shown correctly both times, the 3'-prime end however is located at the third C-atom. In the video both the 5'-end and the 3'-end are indicated at the 5'-end. If you take the left strand (the side of the purple ribbon) of nucleotides you'll find that the 3'-end of deoxyribose is located at the lower left corner of said molecule. Since the saccharides are shown in a Haworth projection it's quite difficult to point out. Here's a not very good Fischer projection of deoxyribose I made pointing it out. Remember, this is the same molecule as shown in the clip, just a different style of drawing it. HOC-CH2-CHOH(this C-atom is the 3'-end)-CHOH-CH2OH(and this is the 5'-end). In an aqueous solution (almost) all monosaccharides (such as deoxyribose) will form to become a circular structure, such as shown in the video.

[@nureileendeannakamaruizam3961]

+NH.-B bealbio.wikispaces.com/file/view/dsDNA.jpg/166732981/350x272/dsDNA.jpg

[@natattacc99]

+nureileen deanna kamaruizam Thanks :)

[@simbananza]

does anyone else find it creepy that this happens in ur eyes. like its happening right now and you dont see it.

[@jonathanmusemeche4865]

+blo shit up Your pupil is just open space covered by the cornea, a multicellular tissue that contains no blood vessels, that's why you don't see it occurring. The nerves behind it detect light and then your brain makes sense of those indications. Not to mention that cells are microscopic and the nucleus is inside of the cell and chromosomes are inside of the nuclear membrane of the nucleus and so on... So then you might ask well how do those cells stay alive without oxygen? Because all eukaryotic animal cells need oxygen for respiration to utilize energy and there are no blood vessels to provide the oxygen. The cornea diffuses oxygen from the tears secreted by your tear ducts.

[@reshmi5333]

+blo shit up hi !! fellow kpopper !! nice to meet a kpopper here

[@Simplebeez]

+blo shit up High Skool!

[@satan4606]

i see it

[@squiddi1393]

+blo shit up You're totally incorrect. First off, the cells in your eye don't actively divide. They are with you your whole life. They are constantly in the G0 phase therefore DNA replication doesn't occur in them and so you wouldn't see this anyways. Replication only happens in preparation for mitosis in interphase, like when you grow as a child or your cells divide and repair your body when you get a cut on your skin, otherwise cells refrain from dividing hence they don't replicate DNA.

[@ryrden927]

To Hank and everyone at Crash Course who helps in creating these videos. I just want to thank you so much on behalf of all of the panicking people who have trouble remembering all of this information. These videos are absolutely incredible! Keep doing what you're doing! :)

[@HiroDoodlez]

Shoutout to Hank for teaching me before my biology test IN LITERALLY 5 HOURS

[@kayeamele]

Keys to being successful as a Pre-Med major: 1) Procrastinate all semester 2) DON'T read any of the assigned material 3) Watch every CrashCourse video the night before an exam 4) Walk into class confidently knowing that you prepared well for the exam

[@sumiatheangel9397]

+kayeamele step 5: panic as you forget half the names of the muscles and bones you supposedly learned the previous year.

[@Ps3COD4Fan]

*CRASH COURSE* _Video notes_ Every body-cell (somatic cell) has 46 chromosomes each containing one DNA molecule *DNA-* Nucleic acid (and so RNA) Double helix *Nucleic acids are polymers* -Many small reprating molecular units -In DNA, these small units are called nucleotides -Put them together and you have a polynucleotide *Nucleotide* -5 Carbon sugar molecule (deoxyribose) -Phosphate group 1- of 4 Nitrogenous base -Adenine (A) -Thymine (T) -Cytosine (C) -Guanine (G) -In DNA sugats and phosphates bond together to form twin backbones Phosphodiester bond -The two strands are anti-parallel -One side goes from 5' ---> 3' -The other from 3' ---> 5' -*5' - AGGTCCG - 3'* -*3' - TCCAGGC - 5'* -These two long chains are linked by the nitrogenous bases via relatively weak hydrogen bonds *Ex:* A-T are hold by a hydrogen bond *Base pairs* -A-T (2 hydrogen bonds) -G-C (3 hydrogen bonds) -Therefore G-C is stronger because it has one more hydrogen bond It is the order or the "Base sequence" that allows your DNA to create you. -*AGGTCCATG* means something completely different as a base p air sequence than, say, *TTCAGTCG* *RNA* *(3 MAJOR DIFFERENCES)* *1.* Single-stranded molecule (nod ouble helix *2.* Sugar in RNA is ribose, which has one more oxygen atom than deoxyribosome *3.* RNA does not contain Thymine (T) instead has Uracil (U) *DNA discovered by Swiss biologist* Friedrich Miescher *Rosalind franklin* X-ray diffraction *Replication* *Helicase*- Enzime Unzips that unwinds the double helix bybreaking hydrogen bonds *DNA Polymerase* -Adds matching nucleotides onto the main stem all the wat down the molecule -Needs a primer, the primer hooks on to so it can start building the new DNA chain -RNA primase provides the primer -The leading strand only needs this RNA primer once at the very beginning -Then DNA polymerase is all, "I got this" and just follows the unzipping adding new nucleotided to the new chain continuously -DNA polymerase can pnly copy strands in the 5' to 3' direction -So there is a problem... the lagging strand is 3' to 5' -RNA primase lays down short RNA primers that gives the DNA polymerase a starting point to then work backwards -Short segments -DNA polymerase can proofread removing nucleotides from the end of a strand when they discover a mismatched base *Okazaki fragments* -RNA primer -These allow the strands to be synthesized in short bursts -And then another DNA polymerase has to go back over and replace all those RNA primers *DNA Ligase* -All of the little fragments get joined up by a final enzyme called DNA Ligase

[@Ps3COD4Fan]

*I've created a set of study flashcards for DNA replication and much more, feel free to check it out, and please thumbs this up so others can use this resource! Study on!* *GO BIOLOGY!* quizlet.com/42951455/bild-1-chapter-13-molecular-basis-of-inheritance-dna-replication-2-flash-cards/

[@Ps3COD4Fan]

***** You don't have to, but they helped me pass University level Biology.

[@dogdemon62]

I just wanted to say I love you. I'm currently taking Bio I and it sucks.

[@Ps3COD4Fan]

dogdemon62 Thank you, but you should change your views about biology or you will never enjoy the subject. If you are able to "like" or be intrigued about biology, you will end up enjoying it and understand it a lot better. Your mood towards a subject is really important.

[@dogdemon62]

I do like biology, it's just the cells are kind of a difficult concept for me to grasp. I love looking at organisms as a whole, and I understand the organ systems very easily, it's just cells I don't get lol. I lean more towards anatomy and physiology.

[@alexandervidal7242]

Got an 83 on my Biology exam :D goodluck to ya!!

[@TheHappyHummy]

You suck I got a 100

[@aimee-hyj]

@@TheHappyHummy higher marks doesn't equal a better person, clearly

[@nathanhe4214]

@@aimee-hyj lmaooo preech

[@emmasabat5926]

@@TheHappyHummy Two can play this game. I got a 112 on my last bio exam.

[@shockstormswag]

6 years later and this is this still gold

[@Jnniesx]

phrase the lord for youtube teachers. Why waste your time reading long ass textbooks and still end up confused when you can just watch a bunch of these videos. These are so much cooler and so much less boring

[@bananimal45]

"the lord is...uh...the lord." ...ohhhhh you meant PRAISE the lord.

[@fmar105]

Jennifer Li I disagree. A textbook will give you a much more in-depth view of such mechanisms than a ten minute video, and will leave you with a much better understanding. I find my textbook challenging and interesting. These videos are great, but they are mere supplements to textbooks and the like.

[@Dstewar25]

my teacher skipped the part where he joked about unzipping jeans so I looked this up to fond out why XD

[@wizardvenom8500]

+Darby Jones seriously? haha. What year group are you in? It's hardly inappropriate lol

[@Dstewar25]

9th and I know right lol.

[@adriennebatty3787]

+Darby Jones Oh my gosh we were learning about this and I'm in an online school so I typed out the joke in the class and my teacher did NOT like it.....it was very awkward for me. I would have died if I was in an actual physical school. But we're in 10th grade, it's not that bad of a joke.

[@inserthere7048]

+Techman shit hide your meth the apocalypse is coming.....like me ;)

[@tiglathpilesariii]

+Darby Jones Me too xD

[@laurenmcshane4628]

Although I only watched half of it and only understood a few parts, the laying out of it combined with my other revision resources finally helped me get the gist of it - you are a star, thank you!

[@firefly-fez]

Props to whoever did the subtitles for this episode, they're hilarious! 😂🤣

[@ageovlove]

This video was perfect for helping me procrastinate on studying for my biology exam. Thanks Hank!

[@ChiaraCami]

The freaking jingle. One of the 1874959 reason why I love crashcourse

[@chium1731]

"it's double helix-citing" i love these dorky puns

[@salahuddeenshaban4054]

when watching this do any of you ever think "How the hell does he know this"

[@dolphingirl1205]

That helicase joke omfg

[@Imogene512]

I will never forget what helicase means now haha!

[@MrMasterDebate]

..this channel is the ONLY reason why im getting a good grade in my science class

[@Mohamed-jv6nv]

Just think how far CrashCourse has come now! Thank you CC and Green brothers for helping me get through my exams

[@metronini]

Hank Green: "Hey, wanna make one" Me "Ok, I'm out!"

[@stoicfloor]

Everyone who studies Biology should watch this.

[@forestriver3282]

im not human I look like one but I have 2 hearts and when I die I regenerate can u do that?

[@sarasawchuk229]

OMG riversong .........."Spoilers"

[@hannahcify]

DOCTOR?? IS THAT YOU?

[@forestriver3282]

no its River ;) SPOILERS!

[@hannahcify]

no!! DOnt spoil it i started the show last week and I'm only on season 3!!

[@JrIcify]

I feel sorry for you people so blinded to the uncommunicatable beauty and wonder of the natural world we live in that you need to go into this fantasy bullshit to release dopamine and/or serotonin in your brains. This reality is so... I don't even know what word to use. It's more fantastical than any MLP or Doctor Who episode you've ever watched. If you could see life as it was, you wouldn't give a shit about those things. I hope one day you awaken to it because I care about you and your happiness. Yes you, the one reading this. I care and wish for you to one day feel the true wonder at life that fantasy and fiction can never give.

[@vladislavapetrova5983]

Their videos have come so far since 2012, from the content to the animation graphics, looking back he is so young and derpy! And here we are, 11 years later he is still saving my butt, from highschool all the way to finishing college. Thank you Hank Green and the team, for helping us get through school in a fun and enjoyable way!

[@rawanmohammad3356]

Watching in 2019, I LOVE CRASH COURSE

[@killianguthrie8502]

I'm in college and I still use these videos. Yep

[@knightndayartificery]

+Killian Guthrie i have my bio 103 final monday. ive been using these videos all semester o-o

[@maryamaitelarbi2674]

i'm in med-school and i use these vidio even tho we study in french not english

[@MrPridizzle]

I'm an astronaut on the international space station and I still use these vids :)

[@sumiatheangel9397]

+Killian Guthrie Same here, and I'll be using them all the way through med school.

[@killianguthrie8502]

Radical

[@Procrastinerd]

Was there an error made at the 5' 3' explanation or am I just having trouble comprehending? Shouldn't the 3' indication circle have been drawn at the third vertice of the pentagonal deoxyribose model?

[@toastysplox5338]

I was thinking that same thing. Maybe because the 5 prime and 3 prime bond to one another and so are shown in the same place? There are suppose to be 2 ester bonds...so maybe the ends refer to the phosphodiester bond on either side of the same sugar. That, if still referring to that first sugar, is still the downstream end of the same molecule. I think it is only mean to refer to a direction. I do not know, though. That was just my rationalization.

[@oxford_phd]

No you're right, there was an error, it should be from the third vertice of the pentagonal sugar, so on top of the phosphate and not below.

[@Procrastinerd]

Hira Javaid Saeed Thanks

[@thelurkingpanda3605]

Hira Javaid Saeed Wow I was so confused by that part, can anyone point me to something that can teach it to me correctly?

[@himanshugupta1566]

Thank you so much crash course...you guys are lifesavers and explain so much from scratch in such less time...love the animation. Pl keep helping us never stop creating

[@nativaconcepcion879]

This is SO good for studying for the TEAS exam. It’s quick n he touches on all the important factors of dna while being a lil nerdy funny..🙏🏽

[@hannie798]

ap exam on monday, anyone?

[@DangerouslyFast]

Same

[@anastasiadancer1]

Yup

[@ailidavid7599]

Hyerin sameeee

[@hydrogeddonn]

Hyerin Yup and the book is basically a waste of time for studying......

[@daaaniphantom]

Hyerin *crying

[@ellensmith8089]

"How is a teenage boy like the enzyme helicase? They both wanna unzip your genes" oh my lord i have not stopped laughing

[@palmalorenzo7778]

this guy has brought me though all my school years, i cannot thank him enough!!

[@timv6141]

Watching this again. Hank is a great teacher! Thanks for everyone who helped make this

[@RickReinster]

I start watching this so I understand my class better, and I end up realizing it's happening ALL THE TIME in my body, so cool!

[@nobeladhikari6602]

i have never understood the 5 prime 3 prime thing...,and probably never will.

[@Androctonus84]

This video won't help with that, since they circled only the 5' carbon on each sugar, but labelled half of them 3'.

[@conceptswithkat3045]

Well if it helps, nucleotides are added to the 3' end because it has a free OH group which reacts to form the bond, so they're being added from the 5' to the 3' direction

[@georgiamitchell3692]

No one understands, not really.

[@dhruboriley2931]

Its chemistry :'3

[@abigailh7223]

Look "5 prime and 3 prime DNA diagram" up on google images. Look at a diagram of a single piece of DNA (as in, not the chain, but one rung of the ladder, made of three parts). It should show that the "top" of each DNA rung (at top of phosphate) as "5 prime", and the "bottom" of each rung (at bottom of sugar) as "3 prime". Therefore, as they chain together, you'll have one side of the DNA helix ladder with all the 5 primes facing up, and the other side of the DNA ladder helix with all the 5 primes pointing down. (and yes, he mislabeled the 3 prime and 5 prime in the video). (Why are these parts of the DNA called 5 prime vs. 3 prime? It has to do with the naming of the Carbons in the carbon rings involved. See W douglas Driver's comment somewhere else under all these replies to NOBEL ADHIKARI for a good explanation...)

[@javierayala1648]

years of trying to understand this from many different professors broken down into only 12 minutes brilliant.

[@AL3X042399]

This cleared up the lagging strand confusion I had and I'm so thankful for this video now.

[@EdilsonJacobSilvaJuniores]

Wow. I thought these videos were good only for high school, but I just noticed you pretty much summed up my first 4-hour Molecular Biology class.

[@alleghenymusicacademy]

When my baby is fussy, putting him in front of your crash course videos calms him.

[@catholonelbridget1072]

This is parenting people. Parenting in its finest.

[@Awgez24]

Give child minecraft to pacify it. Child pacified for the next two decades.

[@coreenthusiast]

Your baby is a nerd

[@JokerMr13]

These are fantastic. Thank you for the uploads! I hope you guys bring back more science episodes

[@gracedonfield1047]

Ok I am here cramming for my freshman bio final only 30 videos to go!

[@rainbowbunchie8237]

Everyone always complains about him talking too fast... It's not that fast at all, you should hear me talk when I'm interested in something.

[@beckylieb2637]

he has a lot of information to cram into a certain space of time, and if your brain has to work harder to keep up... it works harder at everything else... very clever Hank, very clever! make is slower if you need to.

[@weiurdgurl]

The joke Hank makes in the video at 9:25 made me laugh so hard.

[@weiurdgurl]

+Sushil Mario You know how in the DNA replication process the double helix has to unzip. Boys would like to do the same thing with a girls jeans. But sorry that I killed the joke.

[@weiurdgurl]

+Sushil Mario 👍👍👌😆😆

[@isaacmathews4693]

9:22 Lol! :)

[@bobbyalex5705]

He the type of guy who talks to his own cells

[@vilunar5813]

This video was really helpful for me to comprehend DNA and its replication process. I will dare to say that it is the best video I have ever watched about this context on KZbin. Thank you!

[@illikedance106]

Thank goodness for Crash Course. Biology final, anyone?

[@chrissyluvspeace]

who else is cramming for finals week!!

[@beccadavis2287]

My final is tomorrow!

[@liammather3868]

mine is today also, good luck!

[@Retibra]

chrissyluvspeace I'm so screwed I've studied today and yesterday and I still don't feel Congo

[@Retibra]

chrissyluvspeace *confident

[@doublewhopper8689]

Tuesday

[@elisemahar2395]

luv this dude. couldnt pass my tests without him. he has the only non-boring vids

[@fredericavonsiemens6956]

this man is singlehandedly keeping my ap bio grade afloat

[@kieran2blest]

these videos are the best. the editing and detailed number spewing gives us a few specifics we may have missed in individual studies. this "speccy-eyed nerd" has helped a lot of people understand a number of different topics (and has definitely helped me pass a few challenging classes)by showing off his big brains on the internet by describing whatever topic he is needed to, and people like it so they donate and subscribe to his channel at their leisure

[@veronicabursek-krekling6349]

I have a Bio test tomorrow and I'm so confused but this video helped so much!

[@killyourbunny]

+Veronica Bursek-Krekling wow you must be so smart

[@veronicabursek-krekling6349]

+MeepMeepTheMemeCreepBeepBeep I'm sorry, what is that supposed to mean?

[@killyourbunny]

Veronica Bursek-Krekling you dont know what smart means?

[@veronicabursek-krekling6349]

I can promise you that's not it, bye

[@killyourbunny]

+Veronica Bursek-Krekling what?

[@feysalwarsame2829]

Who else is cramming here and other videos because there’s a test coming up

[@alexandercasuga3989]

I love your lectures. It's not boring. Thank you for sharing your knowledge.