Meselson-Stahl Experiment

Paul Andersen explains how the Meselson-Stahl experiment was used to prove that DNA copied itself through a semi-conservative process. They grew E. coli in a medium containing heavy nitrogen (N-15). They then added the E. coli to a medium containing regular nitrogen (N-14) and observed it over several generation.
Intro Music Atribution
Title: I4dsong_loop_main.wav
Artist: CosmicD
Link to sound: www.freesound.o...
Creative Commons Atribution License

[@ucefnasrallah3154]

10 years later and this is still helpful ty

[@king911love]

my final exam is tomorrow ... you were really helpful Mr.Andersen .. and our proffesor he's from Cambridge and only believe in the explain & mention & show & draw questions not a single mcq or t&f or even complete in the tests .. but i got he's attention on the midterms , he said you the only student that got an 96% on his exam , really your videos helped me a lot , thanks let's hope for the best in the final ..

[@driftwood39]

how did it end?

[@king911love]

i got an A .. :)

[@driftwood39]

Doode malood nice :) good luck in your future.

[@king911love]

thank you very much , you too man , that day in the exam as i expected all the questions were short answers and i let my imagination flow and that end up very well , good luck

[@nijamagi1031]

What? Your grammar is atrocious

[@ninilinda95]

Loooooool it took me almost an hour to understand it from my books and i still didnt get it.. and now it took me 5 min just by watching this video and everything is clear 😅😅 thx 👍👍

[@earnitdamit961]

same here bruw

[@kylielawson3271]

@@earnitdamit961 bruv

[@emettvoe9381]

True dat

[@nayumeusa]

incredibly useful for my final genetics exam. Thanks a lot!

[@ufo8mykat]

I've seen this explained a lot of different ways, but this is a nice and concise way of doing it. Answering "What does that mean?" is super important. So is using scientific language for your explanation, prompting students to look it up.

[@jasminesirs2521]

Thank you soooo much. I am doing A level biology and this has really helped me!

[@lemonadethefifthp389]

Thank you! I was panicking because I have a test in less than 2 days about this. Thank you so much for helping me understand this experiment. The simulation helped a lot.

[@kellieashton3697]

GARH! End of semester molecular genetics exam for uni tomorrow and you've just saved my life! Thank you.

[@omaimawasim5396]

I tried to understand this from my teacher 3 times and I couldn't. And once from you has done wonders for me. Thank you!

[@gabriellataylor637]

He explained it better than my professor, thank you!

[@kennielosh]

OMG YOU ARE A LIFE SAVER

[@Ellie-jl3vk]

Takes you 4min to clearly explain this. Took my prof 45min to just confuse the hell out of me. Thank you!!!

[@jerryma6705]

U literally saved me by ur concise and clear language. It does explain everything

[@Alceasy]

Great Video! I love your voice and the calm way you explain everything!

[@cher0924]

Thank you so much! You have cleared my doubts on why nitrogen is used!

[@asensniper]

Very clear presentation, thanks for that

[@michellelarmuseau369]

my friend is from bozeman! love the connections in our world. Her name is minna gomp. Love it!

[@minnagompertz1060]

lmao

[@ashalsaidi143]

you the best at everything. I come to watch your videos for biology, and chemistry. thanks a lot. we appreciate your work.

[@RERGamingorTecdreaminshort]

Its 2021 and this boomer is still helpinggg

[@behayilutesfaye3413]

I am MSc plant breeding student I have an exam advanced genetics, these video help me a lot

[@yoursufferer8794]

Mr Anderson actually explained it so nicely here no other channel made me understand it earlier!

[@musfekaikfatmitu9864]

Heartiest thanks with great satisfaction

[@castleclasher1236]

Thank you for this Video. I was looking for a simple answer to my school homework. I'm from Germany and even I understood the principle now.

[@bikinib6583]

THANK YOU SO MUCH! So clear and such a relief for understanding these complicated topics!!

[@sumayyahaisha2068]

Thanks a lot. This really helped! Please keep making such videos on A level biology.

[@AssasineAngel]

Wow i really liked ur explanation! It was so easy to understand and yet gave all the information i needed!

[@ElnaKruger]

Thank you Mr. Anderson!

[@philr22]

THANK YOU!!! You were the only person to explain this experiment to me, so Thank you!

[@yesthisismew]

you explain so well, every video of you is so good

[@Anonymous-fj2uo]

Honestly I can still Not get my head around this experiment! I've looked on nearly every website+ videos+ text books and I still don't get it. How does it show semi-conservative replication and why did they use bacteria?

[@juggernautknight2749]

Well, this is going to be a very long explanation, but I hope this weird, simplified ''idea'' helps you out: Bacteria is one of the model organisms Geneticists and Cell Biologists use (along with Drosophila, Yeast, etc., these are quick and efficient). We do not want to experiment on our kind. Anyway, this shows the semi-conservative replication because as he stated, bacteria are grown in an isotope that is heavy. So we give bacteria an environment they can adjust to, where they feel good. So they will undergo normal replication, whereas all the DNA is stained with the heavy isotope. So, in this adjusted environment, their DNA is stained with heavy isotopes, and will ''maintain'' these stained strands UNTIL the environment changes. What they did is they used a light isotope, N-14 (or simply Nitrogen). What that means is that the bacteria had to adjust to this NEW environment, by ''taking up'' the N14 (so the bacteria are like: oh, I used to be in a heavy environment, better pick up the light environment too so I can adjust). These bacteria then have combinations of heavy stained strands(lets call it A) and light stained strands (lets call it B). Again, in normal environment, it keeps making AA. AA opens up, replicates, and makes AA again. Why? There is only A available. So, AA splits, and each A ''takes up'' another A. Now, let's add B into the system. AA, replicates, and you suddenly get AB because the bacteria ''adapts'' to the new environment. In other words, one A separates from the other A, and EACH of these ''take up'' a B. This is why we get this combination of AB AB. Now, do one more replication (of AB and AB), split each AB apart and what happens is that Bs will ''move in'' because the bacteria is still in that light environment, hence only Bs keep moving in. So we get: AB, BB, BB, AB (50:50 ratio, semi-conservative) And now, they wanted to see these changes by using a centrifuge. What this means, is that heavy ''things'' will move to the bottom, and light ''things'' will stay on top. So, in Generation 0 (where we only have heavy stains, A) shows that we get a band on the bottom (BECAUSE HEAVY, right?). In generation 1 (meaning we do replication), we get a combination, AB AB because we put these bacteria in a different environment (as mentioned before). We see one band that shows the N14/N15 combination, which is a little bit higher than the N15 band in Generation 0. Still not answering which model it is (either semi-conservative or dispersive can do that). In generation 2, we get AB BB BB AB, so aha! A 50:50 ratio. This shows us that this is semi-conservative. We see 2 bands: A N14/N15 band (because AB presence) and an N14 band (because BB presence.) Long, hope that helps (kind of).

[@aznvietrock]

Cam S b

[@Anonymous-fj2uo]

JuggernautKnight Thank you so much. It did help me get my head around it a lot more! You explained it really well. 'Simple language' is what I needed :)

[@juggernautknight2749]

Glad you understood it!

[@AienBeni]

+JuggernautKnight omg crying thank u for the superb explaination! im really thankful.

[@AfafandMuhammadslovetoyouguys]

I understood through a 4 minute video about a concept I couldnt understand in 12 years of my education lol

[@ffaayyzaah]

The most clear and helpful viedo about expirment thanks a lot

[@sreepriyaa8817]

You are explaining better than my teacher.

[@camilamurillo466]

Best teacher in the whole world!!

[@jasminalves8755]

Super great explanation better than my professor!

[@moon_lit584]

I'm sorry I have to correct you. You said that Watson and Crick figured out the shape of the DNA strand, but it was actually Rosalind Franklin who discovered that...

[@strangelight159]

Ananya Ananth Watson and Crick gave the Double Helix model of DNA in 1953.They Used the X-ray diffraction data by Wilkins and Franclin.Later went onto win the Nobel prize in 1963.

[@VaibhavbBv]

Hey Maurice Wilkins and Rosalind Franklin doesn't figured out the shape of dna it was actually Watson -crick who discovered the shape of dna by using data of Wilkins Franklin experiment

[@crazysox305]

@@VaibhavbBv Yes, Watson and Crick figured out the model with Rosalind's notes, which they essentially stole. The notes Rosalind was writing shows that she had the model practically figured out. They wrongfully used her without giving her any credit, and she passed away before she could receive any rewards of her own. Please understand the history before defending Watson and Crick

[@VaibhavbBv]

Sorry if I was wrong

[@sifexification]

This is very helpful. Thanks Mr Andersen

[@daadaa6356]

omg thank you so much. I didn't understand it a 100% from my books but this made it very clear- Thank you!

[@williamallotey270]

Mr. Andersen u rock🥂

[@seanglossop4777]

This is the only video on KZbin that describes this well :D

[@mmalik1339]

The best explanation I could find on this topic thank you 👌

[@mmalik1339]

@Ashley L N14 was the tag on the original DNA strand. When it was mixed with the DNA tagged N15 it could still continue the replication because the N15 tagged nucleotides were still corresponding nucleotides, the N15 doesn't affect its ability to bind to the original DNA. As for the ratio of the N14 decreasing, its because there was only 2 single strands of DNA tagged N14. When the replicatio happens, the N15 nucleotides are the only nucleotides available for replication to continue hence more N15 strands are being made and so the ratio of N14 to N15 will slowly get larger as there are wayyy more N15 tagged strands than N14 tagged strands over time. Hope that helps xx

[@mmalik1339]

@Ashley L no worries xx

[@somayahbird4527]

BEST EXPLANATION EVER!

[@oreofe8266]

Thanks aa lot! An amazing explanation!

[@the.redwidow]

their are no good videos in German on this but this was really easy to understand thanks!!

[@kallamsamad6736]

Consise and informative. Thank you

[@alessandratallini3117]

Will let you know about my exam! Thanks a lot

[@lucyx8299]

Hi, So I was wondering where the N-14 DNA in the second generation came from because only N-15 DNA was put into the N-14 solution in the first generation. Thank you everyone!

[@SruthiMarkkassery]

Lucy Kay it's actually the other way around. The E.Coli which were grown on N15 medium were transfered to N 14 medium and the data was noted after each ~2o minutes ( time taken for replication by E.coli) .

[@MushroomPerson1]

@@SruthiMarkkasseryfinally an answer after 3 years lol

[@eldrienadsilva3385]

Thank you so much. It's so clear to me, now.

[@LoveScentSensuous]

Thank you so much, this was an excellent explanation!

[@micheleschuler7632]

OMG you just saved my life!! Thank you that was so helpful! You are amazing!

[@tommao6471]

Really good and useful explanation. Thanks!

[@mursyidahxa]

Thank you for this you make the understanding easier!

[@ummahyehmmm7403]

Me : going to call my teacher to explain me this topic while seeing yt has none good vids on this Me sees Bozeman’s vid in this topic : cancels the call

[@sienablier8931]

Thank you so much! This is super helpful!

[@RavenFrostX]

Very good study material! Thank you so much!

[@saltedbrownies]

This video is a Godsend! Thanks you.

[@earnitdamit961]

Yahweh sent

[@carlottaromano3382]

such an easy and clear video of the experiment, thank u so much:)

[@thepunisher3677]

Best video for this experiment!

[@mohammedalsaif4969]

Thank you so much!

[@taylorluvu1]

omg thank you so much, best explanation

[@yujydashine2124]

Science is magical, especially when we have people like you to guide us through every step of the way❤️ helpful video. I can't fathom how grateful I am. Hope you give us more helpful videos❤️❤️

[@anjanarana5133]

Thanks

[@theMedicoholic]

Best explained👍👌👌👌

[@deivibarci2093]

You just saved me one day :) Thanks a lot 🌟

[@chadcapy5403]

thank you very helpful!!

[@madonna4397]

REALLY NEEDED THIS!!

[@adinatrinca7352]

very good video!

[@naralee8707]

awesome explanation

[@Anadance]

Awesome explanation!

[@JULISSALENKAMENDOZAAQUINO]

excelente explicacion muy didactica

[@valengiraldo1234]

Thanks! This was very helpful.

[@somyabothra2966]

great video! very well explained!

[@kanjanaiamsomboon628]

Thank you so much.

[@Gamerlegacy2012]

Thank you this is very insightful.

[@zainabshamma4440]

This is incredibly helpful Thank you so much ❤

[@Shogun973]

i rally wish i seen this yesterday

[@mokgadimaloba6936]

Thank you so much.. this was very helpful

[@jessekahn7525]

Thank you, keep doing what you do!

[@yoirock100]

sir u r d best :D:D :D :D u r just too good...nw i understand evrythng...n m sure it will help in my tmrw's test !! thanq so much

[@harininarayanan2787]

Yeah! I love Mr.Anderson as well! ^_^ He has helped me a lot! Esp that molecular inheritance wala chap! :')

[@yoirock100]

same here!!

[@BHDMusic1]

Greetz from Germany! Thank you ! :)

[@itsmejulia1]

Great explanation, thank you very much for this video!

[@metecheung4663]

Thank you so much because of you I understand now!!!!

[@pungs4458]

The clearest video

[@user-zw9tw4nl4l]

great explanation,!

[@sehrashahzad7078]

Thank you so much 💓

[@kazammarofi8658]

thank you

[@lyraparker5364]

This is great! You can really well explain

[@SamSpeaks00]

thanks. that was very helpful!

[@hodayacohen1589]

Thanks a lot

[@zijihelium1111]

I really appreciate this.

[@zaidshah1955]

thanks for the video but just unsure about one thing, after the 88% to 12% in the end why did you say "if we keep going it will eventually drop off to all nitrogen" 😊 because the two N15 strands will always be there through the generations so it'll never be 100% N14 will it? please let me know thanks

[@SruthiMarkkassery]

Zaid Shah yeah i was wondering the same as well

[@parmisali.8204]

This was very helpful! Thanks!!!

[@dileksimsek8117]

thank you for this animation its amazing

[@shirimazor5636]

very very helpful 😄

[@zayzafoonal-sultani2813]

this is so confusing,

[@ramaos8542]

Thank you!!!!

[@emettvoe9381]

God bless your soul

[@YarroBello]

thank you sir

[@singing.winnie]

Thanks a lot this helped so much..

[@ilkiiny]

Very helpful, thank you!