MESELSON and STAHL - Evidence of semi-conservation replication for A-level Biology. DNA REPLICATION
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- Опубліковано 10 січ 2020
- In this video, I go through the Meselson and Stahl experiment and how this proves that DNA replicates by semi-conservative replication
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finally some Rosalind appreciation love how emphasised on the significant part !!!
OMG!!! U ROCKKK I SWEARR. Our bio teacher had explained this 5 times and no one was able to understand. but this???? WOW!!
aww thank you Salma! So glad I helped you get there with understanding this.
Share with your classmates to hopefully help them too 🤞
5days till mock, gl everyone.. final boost🥹
Poooooo
After watching so many videos on this experiment, I finally got the main idea behind the experiment and got to understand it,thank you so much🙏
Yay 😁😁😁 So glad it helped make it click for you
Honestly, your videos are so helpful. Thank you so much for making them!
You're welcome and I'm so pleased they are helping you so much ☺
You are an actual hero, love you! You don’t understand how helpful these videos are❤️!
awww so happy the videos are helping so much!!!!
Thank you very much mam. You are teaching the concept with basics which is best. I saw couple of videos before. But your video is helpful.
Thank you! Glad it helped
Best explanation I've come across so far, finally understood... Thank you
I'm so pleased it helped!!! 😀 ☺️
most helpful video for explaining how the replication works down the generations ive seen by far!
thank you 😊 Really pleased it was useful.
Thank you so so much you explain it so well!! I was struggling so much to understand it until I watched this.
So pleased it helped you understand 😀
This is the best video for me to understand this experiment! Thank you so much!
You're so welcome, so pleased it helped you understand!
the first time that i could understand the idea after watching so many videos. thank you!
yay! You're so welcome 😁😁
Best explanation I've come across .... miss Estruch 👏👏👏 I appreciate you so much ....
aww thank you so much!!! So glad it helped you 😊😊
@@MissEstruchBiology keep up much love for you ♥️😘😘
Thank you so much! I finally found a video that helps me to understand this
Really pleased it helped you! 😊
Thankyou very much miss. Your videos are so helpful
Thank you! I'm so pleased it's helped ☺️
these videos are so helpful! thank you!
You're welcome, glad they are helping you 😊
I have gone through several videos forthe explanation but non of them helped ,thankfully for the first time i get the best explanation ♥️
Thank you so very much, u've helped me understand clearly
You're very welcome ☺ So pleased that the content is helping you!
Thank you💚the video is really helpful
You're welcome 😊 Glad to hear it helped you
This was incredibly helpful. Subscribed.
aww thank you!! So pleased it helped
thank you for making this! extremely helpful :)
you're welcome! So pleased it helped
omg thank u so so much!! u made this so easy to understand :)
I'm so pleased it helped 😀
This was so helpful...
Thankyou so muchhh💖
So pleased you found it helpful 😀
I couldn't understand this experiment at all but this video helped so much!! Thank you!
That's great!! I'm so glad it helped you get your head around this experiment ☺☺
Thank you soo muchh!! This video really helped me :)
So pleased it helped you 😀
amazing video, helped sm thank you :)
you're so welcome!
Thank you very much .
Absolute life saver!
So happy it's helped you!!! ☺️
Hello Miss
It's a little difficult concept to convey to students.
Your explanation is quite helpful to my preparation of this concept.
Regards 👍
You saved my exams!!!!! Thank you so much :))))
ah wow! I am so happy my content has helped you
Hello Miss Estruch, when do you finish and post the whole spec for AQA A level biology. Your videos are very much helpful
Hello,
All the Y12 content is nearly up and I am working on the final quarter of Y13 content.
I can't put a date on it I'm afraid- I'm pregnant with twins at the moment which are due in September, so this will slow things down significantly on the upload front.
Glad you are finding them so helpful
@@MissEstruchBiology Omds. I didn't know you were pregnant and almost due 😱😱. Please take as much time off and look after yourself xx
@@thelorenzo9719 Thank you :) Good luck with your studies!
thank you
miss.
you're so welcome 😊
Brilliant vid!
Thank you!! So pleased you think so.
BLESS UR SOUL
Hi, great video, so glad have found your channel! Just checking for when it comes to revision, do your videos cover all y12 content? I.e would I cover everything I needed to know for y12 if I revised using your videos, if not, up to which topic is fully completed so I can be sure I’m covering all revision content? Tysm- Olivia
Hi Olivia,
Thanks for the comment, I'm really glad they videos are helping.
Yes, the videos do cover all the theory for Y12. I haven't finished all the maths/practical/exam technique skills videos though, and these are also essential for preparing for the exams.
@@MissEstruchBiology they are, thank you!
And okay, thank you very much, do you know when those ones will be done by? Completely understand if you don’t know.
Also wondering if you know of any other biology resources such as textbooks or flashcards etc you can access/ buy on the internet that you think are useful and good for the aqa a level biology?
@@livharding875 it will be a while. I am finishing the Y13 content for October and then I am going on maternity leave. Therefore the skills will be coming later in 2021 (some practicals/maths/exam tecnique skills are loaded already).
If you have a look at the description on any of my videos I list the books and resources I recommend with links. You can also find this list on my website missestruch.com/new-a-level/
With regards to flashcards, I suggest making your own, and you can see my top 7 revision tips for the best way to make these.
Omg thank thank you so much!!
you're welcome 😊 Hope it helps you
@@MissEstruchBiology it helped me so much that I was hoping to get a question regard this today
You have discussed every basics and fundamental points of Meselson and Stahl experiment and my all the doubts regarding the semi-conservative replication phenomenon have been cleared by you ma'am . THANK YOU SO MUCH .
😁😁 so pleased it has helped you
Exam tomorrow, hope I ace it!!
Good luck!
Hi, do we also need to understand the dispersive model?
Thank u thank u❤️❤️❤️
you're welcome 😊
This can be used for the CIE board as well right?
So in the medium containing 14N, this sample had been growing its own E Coli bacteria too as well as the heavy DNA growing from bacteria in a medium containing 15N?
Is There will be equal possibility ..,for dna n15 to incoprate either n15 or n14 dNA
Do you need to have memorised this for the aqa spec?
I don’t understand at 8:33 why you said there’s one strand of the n14 and one strand of the n15 dna when I thought it was supposed to be two strands for both as shown in the diagram
At 9:08, do all the 4 strands act as templates or just the 2 light strands? Thanks, great video!
all 4 strands
Thank u
aww you're so welcome ☺
fun fact.. crick was on lsd when he discovered the structure of DNA
here before the mock too?
@@m.c.8794 yeep what skl u at lol
bless you
Thank you!!
cheers
Thank you so much for these videos
You're welcome ! Really hope it helped you
Hi miss Estruch!
I have a question regarding the DNA replication.
According to the notes i've been given for this chapter, our teacher mentions that DNA polymerase catalyses the formation of hydrogen bonds between the bases and that DNA ligase catalyses the formation of phosphodiester bonds between the backbones of the newly formed strands.
I've seen your reply on one of the comments saying DNA polymerase doesn't form hydrogen bonds and i'm really confused.
If you can help me out i'd be really thankful! :)
Amazing video by the way, i finally understood the experiment :D
Hello,
DNA polymerase catalyses the reaction to make the DNA polymer (as the name indicates ). The DNA nucleotides are held together to make the polymer by phosphodiester bonds. DNA ligase also forms phosphodiester bonds, but between small sections of the polymer (Okazaki fragments- but this isn't on the spec).
Hydrogen bonds between the bases is NOT catalysed by DNA polymerase. This is heavily emphasised in AQA mark schemes.
Hope that helps
@@MissEstruchBiology yeah, that helped a lot. thank you so much!!
you're welcome 😊
The point where we trnasfer bacteria form N15 medium to N14 medium and collected DNA at various intervals ...after 1or 2 replication we come to know that k n14 beacome incoparte in n15
Hello
You should be able to tell that N14 was incorporated after one division as the DNA would be lighter as one strand N15 and one strand N14.
Hope that helps ☺
Do i actually need to memorise this
Would I need to know about the models and the experiment if I was doing OCR A?
I just had a look at your specification and I can't seem to see it on there
@@MissEstruchBiology Thank you!!
But both time of dna strands are present is not possible that dna n15 stand mixed with other n15 strand instead of dna having n14?
This is why this experiment was conducted, scientists were trying to discover whether DNA replication is conservative (as you describe in this comment) or semi-conservative.
The results showed it must be semi-conservative.
Hi. For the AQA spec do you need to know about purine and pyrimidine?
Hey, no these are not on the AQA spec.
@@MissEstruchBiology Thank you!
What type of question might we get on this? And how can we best approach them?
These would all be application questions.
Most commonly you would be shown the position of the DNA bands in a test tube for some of the generations and then you would have draw in the position of the DNA bands for the next generation of replication.
Or, you could be shown the position of the DNA bands in all the test tubes and then asked to EXPLAIN the position (so talk about the proportion of heavy to light strands of DNA and then explain how this is a result of semi conservative replication).
Hope that helps you.
That’s very helpful :)
Thank you so much! 💙
I get confused with where hydrogen bonds come into this. Does DNA polymerase form the hydrogen bonds between the bases or phosphodiester bonds? or do the hydrogen bonds reform themselves?
Hydrogen bonds hold the two DNA polymer chains together to make DNA a double helix.
DNA polymerase does not form hydrogen bonds. DNA polymerase forms phosphodiester bonds to join together DNA nucleotides to make a single DNA polymer chain.
Hope that helps.
Yes the hydrogen bonds reform themselves
Hi do we need to know about the dispersive hypothesis for a level biology for the aqa spec?
no that's beyond the specification and an application example
@@MissEstruchBiology okay thank you 😊
Thank u for these videos im failing so this is my only hope loool
You got this! Good luck
Is there a copy of replicated DNA founded early and then they tried to find the appropriate way to reach it or what? they compared their results with what?
Hello,
I'm not sure exactly what you're asking.
They isolated DNA from bacteria, allowed it to replicate and then compared the position of the DNA in the test tube pre and post replication.
Hope that helps
Video starts at 5:56.
Hi sister, pls tell me is it edexel?
this is for AQA
I had a question can i ask
Hello, ask away 😊
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Remember be careful and stay safe.
11:00
can i have your power point?
Hi,
All my PowerPoints are on the Miss Estruch Biology TES Shop.
ugh I still don't understand.. someone needs to explain this to me in dummy terms
If you have any questions that might help you understand then ask away
@@MissEstruchBiology I understand the part until 8:45.. why do they need a replicate another time, hasn't semi conservative replication happened already, like there is a original strand and new strand already formed?
Hello, yes you are right it had. But then semi-conservative replication happened again so that even more cells could be made. This whole experiment is continual replication making more bacterial cells, not replication continually happening in one cell.
I hope that helps.
my teacher overcomplicated this so much
Glad it was more straightforward 😊
Actualyy i am pakistani and i cant breif my question in english
Hello,
Thats OK, I'll try my best
Thank you so much why did i only see this now..i had the biggest concerns on this istg! 8 days till paper 1 🫠