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I have just studied DNA Replication for my Biology Class and I have this question that leaves me stuck, though I have tried to figure it out myself.

During telomere replication, I am aware Telomerase elongates the 3' end of the template strand on both molecules and then DNA repair Polymerase comes in to fill in the gap that could not be previously synthesised after the last primer. After this is complete, we would have the T-loop formation and Shelterin complex arrangement to protect these ends and form what we know as telomeres. However, if we take both DNA molecules, this only happens at one end of each of them, right? As the other end would correspond to the leading strand.

So I am confused: do telomeres just appear at one end of the chromosome?

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  • $\begingroup$ The term "leading strand" only makes sense in the context of a gene. Both strands can contain genes, it only depends on where is the promoter. I think this is where your confusion comes from. So, correcting your question you were probably looking for to the 5'->3' strand and the 3'->5' one. As both ends have both strands (one's 5'->3' is the other's 3'->5'), yes, telomeres appear at both ends. $\endgroup$
    – FloriOn
    Apr 18, 2017 at 17:41
  • $\begingroup$ Ah, okay, I see. In my class, we did not see any specificity as to replication being made about a gene but rather as a whole strand, so I just figured that for a 5'->3' strand, every left replication fork would give rise to a continuously synthesised strand and the right one to a lagging one. $\endgroup$
    – Bee
    Apr 18, 2017 at 19:17
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    $\begingroup$ This answer might help you (if you’re still interested in getting help 2 years later). You’re right that this has nothing to do with genes. $\endgroup$
    – canadianer
    Jan 4, 2019 at 20:07

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This is a great question! The issue- the "paradox" of replication of linear chromosomes- of trying to filling in the unreplicated region (an overhanging 3' end) should technically be an issue only for one 3' end of each chromosome on any round of replication, as one new 3' end is produced by leading stand synthesis, and the other- the one with the issue- by lagging strand synthesis. However, both ends will have telomeres, they simply trade off being the end with the issue, in each round of replication. Or you could say, in a single round of replication, one sister will have an issue at the right end end, and the other sister will have the issue at the left hand end.

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  • $\begingroup$ Welcome. Can you add sources? $\endgroup$
    – AliceD ♦
    Dec 8, 2018 at 11:58

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