I never comment on videos, but this is an absolute GODSEND. I am a college biology student and I never really knew what this experiment meant until just now, sadly enough. You make it easy to understand. You've saved me in biochem and now bio. Thank you thank you!
Hey Andrei , I just want to say Thank you because I've been watching your lectures for such a long time and they have been life savers for my studies. You have such a great talent for teaching any topic with an outstanding confidence and fluency that it amazes me every single time I watch your videos. Also, I wanted to point something out , around the 4:15 time mark you said that the bacteria contained in the medium divided by mitosis but that is not correct since bacteria divide by the process of binary fission, it's not a big deal but still is worth mentioning.
Thank you so much for this video! I never thought I'd get my head around this but your clear explanation has helped massively - I now understand! Thanks for sharing.
Thank you for delivering appropriate detail so efficiently!!! Words cannot adequately express my gratitude for your lectures. You have a true gift organizing information and relaying it to those seeking material mastery. I am certain you are a significant reason many talented medical professionals, scientists, and the like are doing good in the world (the foundation you lay out is the strongest of scaffolding). THANK YOU for sharing your gift of insight!!!
Hey Andrey! I have been following your videos from undergrad. Now I am in grad school, yet here I am. 😉 However, it's so bad that ever since I have not taken a moment to thank you. Hence, I would love to say THANK YOU for your videos! You explain complex concepts in the most understandable form. THANK YOU once again!👍 I wish you the best in all that you do.
I got a little distracted by the marker trick :P But I love your lectures: the pace at which you teach, the detailed explanation, and the way you already write things down before the video and then narrate it in your own words! lots of love and gratitude!
@@AKLECTURES Assalamo alaikum sir!!! I am your big fain . I wish you always glow like a biggest star on the sky and May Allah fulfill your all wishes before you pray for them. You are a great teacher. Lots of respect from here.
N-15, a very interesting rare (heavy, non radioactive) isotope of nitrogen with an unbelievable small thermal neutron capture cross section of 0,024 millibarn. Used in nitrogen-15 NMR because of the fractioned nuclear spin of 1/2.
Excellent explanation as always but at 9:12 i believe it is not radioactively labelled isotope but it is (N 15)more denser isotope right? And we separate them based on densities that’s why on the photograph the band is towards right due to more gravitational force
The first generation band appears to be less dense than that of the original sample, but the corresponding text says that the single band is denser than the original band. It seems to me that the single band should be less dense because of addition of N-14. Is the picture right and the text wrong? Or am I misunderstanding?
It is done to maintain equal distance between the nitrogenous bases as they are paired in a complementary manner. Notice the structures of the purines and pyrimidines and you can see why there is a double bond between Adenine and Thymine and a triple bond between guanine and cytosine. Between Adenine and Thymine there are two atoms of either nitrogen or oxygen on each. This means only two hydrogen bonds can be formed. (H bonds form with very electronegative atoms such as F, O, N, Cl) In case of Guanine and Cytosine, there are three atoms of nitrogen/oxygen on each. Thus, three hydrogen bonds.
Why aren't the newly synthesized strands semiconservative as well? Why are they purely new? Is it because only N-14 and N-15 isotopes are being used? Hypothetically if N-13 was in the mixture, would the newly synthesized containing only N-14 be semiconservative, like the parental strands containing N-14 and N-15?
There was no N-13 in the mixture. N-13 is not a stable isotope, it has a half life of ten minutes. Replication is always semi-conservative. For subsequent rounds of DNA replication only N-14 were made available to the bacteria. N-15 was only made available to the bacteria at the beginning.
hello! i am from India, I'm 16 and I'm a high school student and your lectures are my life savers! you explain it so well! and so precisely! i really love you sir!
He mentioned in the video. The nitrogen was utilized to form the nitrogenous bases, sugars, etc. that need to be synthesized during DNA replication. The nitrogen with the radio label was incorporated into those factors (bases, sugars, etc.) of the newly synthesized strands so they could be measured using density centrifugation. The isotopes of nitrogen, that act as radiolabels, have different densities.
Sir your teaching is very usefull but i request u sir plzzz what u write in the board we can't see it's not clear to note that so plzzz write little big size sir plzzz it's my humble request u sir
That is true, the bacteria replicate via binary fission. I guess it was a bit of a misspeak when he seemed to imply this only applies to mitosis. Semi-conservative applies anytime DNA replicates.
man! can you make a video on how to do that thing you were doing with the marker in the beginning?
lol ,exactly why i came to the comments in the first 5 secs.
@@phoenixCorp_KE me tooo
I never comment on videos, but this is an absolute GODSEND. I am a college biology student and I never really knew what this experiment meant until just now, sadly enough. You make it easy to understand. You've saved me in biochem and now bio. Thank you thank you!
This is a good lecture but please note that nitrogen-15 is not radioactive - it is a stable isotope of nitrogen.
Hey Andrei , I just want to say Thank you because I've been watching your lectures for such a long time and they have been life savers for my studies. You have such a great talent for teaching any topic with an outstanding confidence and fluency that it amazes me every single time I watch your videos. Also, I wanted to point something out , around the 4:15 time mark you said that the bacteria contained in the medium divided by mitosis but that is not correct since bacteria divide by the process of binary fission, it's not a big deal but still is worth mentioning.
They reproduce using binary fusion
This presentation is as clear as a black night sky over the Arctic wilderness.
Thank you so much for this video! I never thought I'd get my head around this but your clear explanation has helped massively - I now understand! Thanks for sharing.
Gotta love Meselson and Stahl! Best lectures-go you!
Katia Kyriakoulis yes! brilliant folks! and thank you! :)
Thank you for delivering appropriate detail so efficiently!!! Words cannot adequately express my gratitude for your lectures. You have a true gift organizing information and relaying it to those seeking material mastery.
I am certain you are a significant reason many talented medical professionals, scientists, and the like are doing good in the world (the foundation you lay out is the strongest of scaffolding).
THANK YOU for sharing your gift of insight!!!
Hey Andrey! I have been following your videos from undergrad. Now I am in grad school, yet here I am. 😉 However, it's so bad that ever since I have not taken a moment to thank you. Hence, I would love to say THANK YOU for your videos! You explain complex concepts in the most understandable form. THANK YOU once again!👍
I wish you the best in all that you do.
Really helpful and clear explanation! Thank you so much ! I finally understand this. :)
I got a little distracted by the marker trick :P But I love your lectures: the pace at which you teach, the detailed explanation, and the way you already write things down before the video and then narrate it in your own words! lots of love and gratitude!
I didnt even notice the marker thing until you just pointed it out hah but thanks for your kind words! Glad to hear that its helped you!
Please keep doing the marker thing. It's so cool!
@@AKLECTURES Assalamo alaikum sir!!!
I am your big fain . I wish you always glow like a biggest star on the sky and May Allah fulfill your all wishes before you pray for them. You are a great teacher. Lots of respect from here.
Your lectures are easy to follow and are amazing!
N-15, a very interesting rare (heavy, non radioactive) isotope of nitrogen with an unbelievable small thermal neutron capture cross section of 0,024 millibarn. Used in nitrogen-15 NMR because of the fractioned nuclear spin of 1/2.
I just wanted you to know that your videos are still so relevant and are saving me in this semester's biochemistry course
Thank you, this explanation was so clear I now understand!
Well explained. Thank you!
love it! thank you so much!
This man is carrying me through my MCAT studies. Thanks mate!! Wish me luck this upcoming application cycle
Umakwana gee
Awesome video man, I appreciate it.
this was so helpful thank you!!
A simple and clear explanation given. Thanks.
splendid lecture!!
thank you!
Thanks a lot .
Very clear! thank youuu!
sir you are amazing thank you! making my a levels a piece of cake
Thank you, now I am clear
Great work......do it continuously
تالله اني أحبكم يا قروب المطانيخ😭❤❤❤❤❤❤
thanks very well explained
thank you so much
Great job 👍👍👍
Really ,very helpful
Well described and really helpful 🙂
Goodddddd.....easly and simple way to tech....bestttt
Wonderful
Excellent explanation as always but at 9:12 i believe it is not radioactively labelled isotope but it is (N 15)more denser isotope right? And we separate them based on densities that’s why on the photograph the band is towards right due to more gravitational force
Sir you are a great teacher
why should we use only T radiocatively labelled T? is it to measure only replication and not transcription?
Thank u soo much sir!!!!!!!!!!!!!!!!
you are sooo good sir
4:16 Bacteria don't undergo mitosis, but only binary fission.
Is it required for the mcat?
Damn it! You are such good😂
Hatsoff👍👍
splendid
The first generation band appears to be less dense than that of the original sample, but the corresponding text says that the single band is denser than the original band. It seems to me that the single band should be less dense because of addition of N-14. Is the picture right and the text wrong? Or am I misunderstanding?
After DNA replication , the density of their DNA had DECREASED to a value intermediate between 14N and 15N
waooo i mean just waoo...u explained soo well literally...thankyou sir 👏👏👏👏
can you give the reason that why the double bond occur in between adanin and thymine and three Bond between glycine and cytosine?
It is done to maintain equal distance between the nitrogenous bases as they are paired in a complementary manner. Notice the structures of the purines and pyrimidines and you can see why there is a double bond between Adenine and Thymine and a triple bond between guanine and cytosine.
Between Adenine and Thymine there are two atoms of either nitrogen or oxygen on each. This means only two hydrogen bonds can be formed. (H bonds form with very electronegative atoms such as F, O, N, Cl)
In case of Guanine and Cytosine, there are three atoms of nitrogen/oxygen on each. Thus, three hydrogen bonds.
Why aren't the newly synthesized strands semiconservative as well? Why are they purely new? Is it because only N-14 and N-15 isotopes are being used? Hypothetically if N-13 was in the mixture, would the newly synthesized containing only N-14 be semiconservative, like the parental strands containing N-14 and N-15?
There was no N-13 in the mixture. N-13 is not a stable isotope, it has a half life of ten minutes. Replication is always semi-conservative. For subsequent rounds of DNA replication only N-14 were made available to the bacteria. N-15 was only made available to the bacteria at the beginning.
hello! i am from India, I'm 16 and I'm a high school student and your lectures are my life savers! you explain it so well! and so precisely! i really love you sir!
very well explained. please explain the dispersive model as well.
Can I ask i’m really clueless, why was Nitrogen used??
He mentioned in the video. The nitrogen was utilized to form the nitrogenous bases, sugars, etc. that need to be synthesized during DNA replication. The nitrogen with the radio label was incorporated into those factors (bases, sugars, etc.) of the newly synthesized strands so they could be measured using density centrifugation. The isotopes of nitrogen, that act as radiolabels, have different densities.
In 1st generation it is written the band was denser than original one.Perhaps it would be less denser
Sir your teaching is very usefull but i request u sir plzzz what u write in the board we can't see it's not clear to note that so plzzz write little big size sir plzzz it's my humble request u sir
Superb explanation sir me from India greatly influenced by ur teaching style....very helpful
Wow
I thought they reproduce via Binary Fission
That is true, the bacteria replicate via binary fission. I guess it was a bit of a misspeak when he seemed to imply this only applies to mitosis. Semi-conservative applies anytime DNA replicates.
Too long!
Thanks a lot .