請教一個有關telemore的問題：
在真核細胞中常用telomere來解決DNA複製時5'end的問題。
所以有人說telomere就像一個分子時鐘，用來控制細胞可
以進行分裂的次數。我想請教的是：
(1)以人類來說，是否體細胞在分化完成後，其telomerase
的基因就不表現，而使其telomere不再增長，反而隨
著細胞分裂次數增加而變短呢？那體細胞telomerase
activity 被turn off時，當時的telomere有多長呢？
(2)是否隨著細胞的分裂，telomere不斷變短，直到telomere
完全被消耗殆盡，細胞才失去再分裂的能力？或者
telomere長度短到一個threshold length時，細胞就不
能在分裂了？若是如此，那此threshold length是
多長呢？
(3)以人類體細胞而言，每分裂一次會使telomere減少
幾個base呢？
因為小弟看了一些相關paper，但其說法有些出入，故想在此
請教各位高手，請不吝賜教，感激不盡！！
--
※ Origin: 楓橋驛站<bbs.cs.nthu.edu.tw> ◆ From: lstst1.life.nthu.edu.tw
> -------------------------------------------------------------------------- <
發信人: lai01usa@nospamnetscape.net (T7 Phage), 看板: Biology
標 題: Re: 請問telomere......
發信站: FASTNET(tm) PA/NJ/DE Internet (Thu Nov 19 14:40:37 1998)
轉信站: Ptt!news.ntu!spring!howland.erols.net!newsfeed.fast.net!news.fast.net!
In article <3RXMQZ$IXU@bbs.cs.nthu.edu.tw>, chemo.bbs@bbs.cs.nthu.edu.tw (晨曦中的微風) wrote:
> 請教一個有關telemore的問題：
>
> 在真核細胞中常用telomere來解決DNA複製時5'end的問題。
>
> 所以有人說telomere就像一個分子時鐘，用來控制細胞可
>
> 以進行分裂的次數。我想請教的是：
>
> (1)以人類來說，是否體細胞在分化完成後，其telomerase
> 的基因就不表現，而使其telomere不再增長，反而隨
> 著細胞分裂次數增加而變短呢？那體細胞telomerase
> activity 被turn off時，當時的telomere有多長呢？
>
I think it depends on cell types because the telomerase activity could be
different in different cell types, and thus the lengths of telomeres could be
different too.
> (2)是否隨著細胞的分裂，telomere不斷變短，直到telomere
> 完全被消耗殆盡，細胞才失去再分裂的能力？或者
> telomere長度短到一個threshold length時，細胞就不
> 能在分裂了？若是如此，那此threshold length是
> 多長呢？
I do not think telomere can be completely lost before it dies. Before
telomere is completely lost, it will activate other gene(s), and thus activates
reactions such as apoptosis. The mechanisms? I do not know. :)
> (3)以人類體細胞而言，每分裂一次會使telomere減少
> 幾個base呢？
I think that in theory the loss will be the length of the RNA primer.
>因為小弟看了一些相關paper，但其說法有些出入，故想在此
>
>請教各位高手，請不吝賜教，感激不盡！！
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> -------------------------------------------------------------------------- <
發信人: coiled.bbs@bbs.ntu.edu.tw (嗯...酷酷的喔), 看板: Biology
標 題: Re: 請問telomere......
發信站: 台大計中椰林風情站 (Fri Nov 20 13:30:51 1998)
轉信站: Ptt!news.ntu!Palmarama
Telomerase knock out mice showed almost normal phenotypes that telomerase activity
may not play a crucial role in cell proliferation. But before you accept this
concept, please concider two points:1. Mouse cells are some different from
human's. Mouse cells have higher potential for proliferation. 2. There are other
mechanisms involved to maintain telomere length, such as recombination.
Analysing cancer cells also showed very heterogenious result of their telomerase
activities.
It's still not so clear about telomere now...and recently many groups present
many controversal results...that's really interesting!