Added: 2 years ago
From: garlandscience
Views: 167,585
Sort by time | Sort by thread (beta)

Link to this comment:

Share to:

All Comments (193)

Sign In or Sign Up now to post a comment!
  • So clear and concise. Thanks for finally making me get this mechanism in time for tomorrow's biochem exam.

  • @Biospark88 hey! I have a biochem exam today, too! lol maybe we're in the same class...

  • @anniebasic Are you in 153B at UCLA?

  • @Biospark88 Yes. With chanfreau... Our exam is in ... a couple hours lol 

  • @anniebasic Yep, its me, Brett. Small world isnt it?

  • @Biospark88 ...where do you sit? Small world? More like desperate biochemistry majors coincidentally agreeing that the TAs suck at explaining telomeric activity. lol

  • Nice explanation,thank you for sharing

  • Is it just me or does this look too much like something made this thing?

  • <3 this video

  • Like if you only came here because of RP mcb ws!!!! xDDD

  • great explanation!

  • RP FTW!

  • Thank you...!!!!

    

  • I hate it when I try to pause a youtube video by clicking space, the page moves downward.

  • Thank you!!!

  • Comment removed

  • very clear thanks!!!

  • Oh My GOD!!! this is fantastic! i cant believe i spent 40 minutes trying to read about it!

  • In the end, the lagging strand (which is longer) forms a T-loop, showing that the chromosome is finished. This serves as a protection against losing information, prevents chromosomes to bind to each other and so on. The thing to remember is that telomerase is very often inactive on somatic cells, which means that those chromosomes shorten every time they replicate. This is why we die of age. Cancer cells and stem cells have active telomerase (which is why cancer just keeps on growing).

  • @nattenshora It's interesting. Naked mole rats have a lifespan of 30 years.. compared with 5 for a common rat. The difference? Naked mole rats have active telomerase. Now why they don't have uncontrolled cell growth I don't know...

  • then what happens? is the lagging strand longer in the end??

  • @zyferion I don't think it is longer because remember, each chromosome has to have a telomere i.e. a few bases which later fold back on to the chromosome to protect it from things like nuclease and so on. So am thinking those extra base would have to act as the telomeres. I might be wrong though.

  • SO INTERESTING!

  • Thank you so much for the movie, I was like WTF during the lesson at school

  • Someone answer me? Is telomerase a type of reverse transcriptase? Thanks!

  • @hematitecrow I hadn't thought of that before, interesting. I can't say for sure but it would seem so, since it's an enzyme that uses RNA to create DNA, which is pretty much the exact description of a reverse transcriptase. In my bio class we only talked about reverse transcriptase in retroviruses though, so I'm not sure if it is or not. Sorry, I didn't even answer your question. I just got really excited that I understood what you were talking about and why lol.

  • @hematitecrow Not the whole telomerase, just a subunit of it has that ability. So, in the video, the part where the DNA template strand is elongated, that would be the protein/enzyme subunit of telomerase acting as a reverse transcriptase i.e. the enzyme subunit is transcribing it's single RNA strand into a single DNA strand. Hope that helps.

  • @RobinahJ okay, thanks :)

  • @hematitecrow my pleasure babe :)

  • Hi! Ok just for more precision , In humans the Telomere repeat sequence is TTAGGG and thus the RNA template within Telomerase would be sequnced as AAUCCC.

  • @michiyo1986 No the 'U' wudn be in it bcauz is a new DNA strand thats being formed and not RNA. kul (Y)

  • @lovestuck4444 He's referring to the RNA sequence inside the Telomerase enzyme. It has a AAUCCC sequence. The telomere is the DNA part that has 5'-TTAGGG-3' repeat seq. Right?

  • better explanation that my professor or my $200 text book. THANK YOU.

  • Very helpful to see it explained like this! 

  • Even if you already understand it, this will make you never forget it anymore!

  • why do professors suck so much!!!!!!??????

  • great video

  • thankgod my prof decided to show it in class rather than trying to explain in still pictures...things are just so much better in motion

  • duh

  • Thanks heaps, so useful, finally get it :)

  • Believe it or not that video explained the main idea better than stryer's book!

  • This concept for some reason always confused me. Thanks!

  • thx. This video make it easier to understand :)

  • saweet!

  • but this is not the case for somatic cells...

  • Umm I dont know alot about this but, how reliable is that enzyme i mean whats the chance of it not letting it do a mistake in %

    Cuz no mutation is needed.

  • thanks

    

  • that make sense !!! OH YOUTUBE WITHOUT YOU HOW CAN I UNDERSTAND GENETIC ??

  • that make sense !!! OH YOUTUBE WITHOUT YOU HOW CAN I UNDERSTAND GENETIC ??

  • Computers run on binary code, using Boolean mathematics. Real life runs on Quaternary code using ________ mathematics. Once we get quaternary code (CGAT as opposed to 0,1) down to a T, we can program DNA to do exactly what we want. This telomere basically copies and pastes some lines of code and does some natural Quaternary arithmetic by the way I see it.

  • Really good video. Thanks

  • Good video. Damn book mentions this but gives a different picture!

  • doesnt telomer units consist of 'TTAGGG' and not 'TTGGGG' as shown in the video?

  • @hellopanda27 this is not human telomere lol

  • this was very helpful!

  • i would do her soo bad because of this video

  • why go to school when you can just youtube it?! :D

  • @martina092092 Because unfortunately youtube won't give us a diploma :(

  • Thank you. Simple but effective

  • I have a question: Does a similar mechanism work at the 5' end of the leading strand? The replication of the leading strand also starts with a RNA-primer, which is removed after replication has started. So you would end up with a slightly shortened strand at that end.

  • Great video!

    Thank you.

  • Do any one have some good articles regarding this telomere? share it to us please.. thanks =)

  • Youtube is now officially a lecturer on my course

  • Comment removed

  • great and helpful vid

  • Thank you!!!

  • If this were so, and telomerase is active in all cells, cellular senescence wouldn't exist! The Hayflick limit wouldn't exist! DNA stops replicating after its telomeres have been completely eliminated through multiple rounds of replication (and thus the cell w/ out telomeres can no longer divide.) Cuz telomerase activity has definitely been linked with uncontrolled cell division and metastisis!!!!

  • But this isn't accurate, though, is it? From what I understand, the genes for telomerase only are expressed (and thus telomerase only exists) in stem cells and cancer cells.  This video makes it sound like telomerase is active in every cell, and that it is normal for the telomeres to be lengthened after every DNA replication.

  • @1092jniufvhorh I think that telomeraseactually is active in all cells, but it's 10-20 times more active in cancer cells which is why they are able to spread with ease as they are not 'breaking down' as fast.

  • @Bowlesy13 Can you link me to an article that shows telomerase activity in all cells?

  • @Azel247 On your channel Mate

  • omg thank you so much for that video, i now have understood this part for my finals next week!!!

  • if the parent strand was extended, don't you still have the same problem as before, namely, that Pol alpha still doesn't have a 3' OH to work with when completing the 5' end of the new strand?

  • @cubixguy77 Yea, that is true, but the telomere section is a lot longer than what they showed on the video. So while it would shorten at every replication, because the telomere section is useless, we don't lose any valuable parts. They say with aging, our telomeres get shorter and this might be one of of the reasons for making bad proteins due to the gene section getting cut off. Hope that helps.

  • Comment removed

  • Almost totally correct. except that you can't just start the rna primer at the 5' end, so the lengthened 3' end actually bends around to the other side to beable to rna prime. I was wishing the video would've shown this. :( Thanks for posting though, still quite helpful!

  • SO HELPFUL!!

  • perfect!!!!

    thank

  • TTAGGG is the sequence in humans however the TTGGGG is the sequence shown is from tetrahymena the organism which most of the telomerase studies are performed on.

  • thanks

  • THANKS!!!

  • awesome

  • If you can help me you must be good Thanks : )

  • Eureka !

  • 일미 시험 잘봐라

  • thanks you very much

  • am i wrong or does this end-replication problem exist for the beginning of the leading strand too where a RNA primer would also be needed to initiate replication?

  • @DeadHelena no, because replication is initiated in the middle of the DNA molecule, and proceeds out toward the ends in opposite directions

  • Comment removed

  • @cubixguy77

    I had the same thought as DeadHelena. Thanx for clarifying that .

  • @cubixguy77 Replication starts at many different spots along a Dna strand not the middle. Only in Prokaryotes does it start in one spot, but they have circular Dna anyway.

  • thanks

  • thank u for posting this video

  • Hvala puno! Thank you so much

  • Thank you so much! I couldn't find the simple answer to "how is telomer replicated," even in my General Genetics textbook! Stupid publishers.

  • Comment removed

  • This is fabulous!

  • what about at the 3' end of the 3'-->5' parent strand? isnt an RNA primer used at that end as well? how is that converted to dna? or is there a telomere there too?

  • Thank you very much for this video!

  • :D love it!

  • Oh thank God. This video accomplished in 2 mins what all my prof's couldn't accomplish in hours.

  • @FudgeStain Youtube saves everything haha

  • @FudgeStain exactly wow thank God for the uploader

  • thank you!!! i unerstand now!!! ;)

  • what. x,x

  • I get it nowwwwww!!! awesome vid!

  • thaaank you so much

  • Thank so much for this video! Reading the book didn't make sense. = )

  • Great vid

  • loved the videoo .. helped me a lot during revision !!

  • ooooh, i get it now

  • i hate to say this but to be honest i still don't understand. at 0:29 why can't the dna primase add the rna primer. and from that OH group, allow dna polymerase 3 to bind and extend to form the complete strand just like 1:47? please help thanks.

  • at 0:37 why can't dna pol 3 bind to continue it?

  • @Catchetat the purpose of the primer is to make an indication and "tell" the nucleotides to start binding there. Without the primers, the nucleotides would not know where to start binding.

    An analogy would be like this: you're given a stack of paper to photocopy. The person says he already photocopied some of the pages. You won't know where to start again unless he puts a note or make a mark to tell you where you should pick up from where he left off.

  • @kitcatwin yes i get that but if you see 0:45 and 1:45 is essentially the same... the gap is just lengthened.

  • This video was a great help!

  • Very clear!!

  • AWESOME!!!!!!

  • But that leaves the other new DNA on the bottom shorter than the one on the top.

    Right?

  • Biology should totally be a visualized course with tons of simple and amazing videos like this. Otherwise, you just don't get it even you read the book for 1000 times!

  • Excellent animation!

  • Fantastic Job

  • The good and bad of protecting teleomeres:

    Good: May help with aging, and may live longer

    Bad: Would destroy the self destruct mechanism in cancer cells, thus may increases risk of cancer.

  • LOVED IT THANK YOU *THUMBS UP*

  • wow thanks for the vid

    made it so much clearer :)

    thanks again

  • thx. helped me lot

  • THANK YOU SO MUCH I WAS SO CONFUSED,

  • this is amazing... thanks so very much..

  • I have a question, cansomeone answer me please? Is telomerase enzyme active in all cells?thank you

  • No its only active germ cells, stem cells and certain immunological cells forgot which ones tho

  • Thank you so much for your kind reply. It was very helpful.

  • As far as i know it is active in germ cells (sex cells) and i believe the thymus gland if i remember correctly where certain stem cells exist. All cells have a recessive phenotype for telomerase production, just switched off, the problem is when normal cells go through a bad mutation which can turn it on, then it can make it immortal, this is what causes cancer. Hope it helped a bit.

  • @01101100d thank you so much! Neithe rmy bio teacher nor this annoyingly basic and uninformative video were abloe to make that clear to me! Your explanation is clear and informative =)

  • yay! i understand much better w this video..thank you so much! now im off to my first molecular biology test of the semester....and i feel a lil better about it =D

  • Wow, endlich gecheckt. Danke!

  • not TTAGGG? 

    I read that telomer has 2000folds sequence of TTAGGG.

  • TTAGGG is specific to humans. The conserved sequence may vary between species.

  • To answer slimsephy's question, because in normal cells the enzyme telomerase is inactive. The consequences of that you can think for yourself. In some cancer cells this enzyme is reactivated by yet unknown means. Thats partly why they can divide indefinitely

  • I...kind of get it... O.o

  • Very helpful video! Bio teacher wasn't clear about why lagging strand becomes short and so the resulting need for Telomerase.

  • So why do the ends of telomeres get shorter?

  • Telomeres get shorter only in somatic cells. Take a look at your germline cells and you'll notice that the telomeres are longer. I believe that this is because telomerase is strongly expressed in germline cells while not in somatic cells.

  • And I swear that the RNA primer is left on the leading strand since it DNA synthesis towards the replication fork from the 3' end of the template strand. After DNA polymerase I removes the RNA primer on the end of the leading strand, there is no properly paired base before the end (no 3' on leading strand to continue from) to allow for the synthesis of DNA by DNA polymerase I.

  • This video doesn't make sense. doesn't DNA polymerase III read the template strand from 3'-5'? So if the replication fork is to the left of the ends (as it should be) the leading strand would be replicated off of the upper template strand. Also, wouldn't the lagging strand synthesize DNA all the way to the end, away from the replication fork, since there is the 3' end from the RNA primer to start from?

  • One question, what about the rna primer on the leading strand????? i don't understand how is replaced.........thanks

  • The replication origin is not at the end of the DNA, and synthesis occurs bidirectionally from that origin. So the primer on the leading strand is replaced by synthesis from the 3'OH of the lagging strand that extended from the other side of the replication origin.

  • Isn't the six-nucleotide sequence TTAGGG?

  • yup

  • Haha! Nice catch! ;(

  • Ooops, wrong smiley... XD

  • Yes

  • Yes, but only with vertebrates. There are several variations of the telomeric repetition sequence. The TTGGGG-ending is the one of ciliates.

  • It is in the human genome, but this is probably of Tetrahymena, which has a different telomere

    sequence. The mechanism is the same for most organisms, but the sequence varies.

  • Alright. Got it, thank you. Good video though.

  • In the human genome :)

  • @Puddy88 It is not always the case, there are some exceptions. But for all intents and purposes (tests pretty much) TTAGGG is the repeating sequence

  • @Puddy88 .....Yes, in humans it is. This example is correct for tetrahymena, and other simple euks.

  • Comment removed