Register | Sign In


Understanding through Discussion


EvC Forum active members: 65 (9162 total)
4 online now:
Newest Member: popoi
Post Volume: Total: 915,815 Year: 3,072/9,624 Month: 917/1,588 Week: 100/223 Day: 11/17 Hour: 0/0


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   The Mystery of Stop-Codons....
semilanceata
Junior Member (Idle past 5288 days)
Posts: 12
Joined: 04-21-2008


Message 1 of 14 (463859)
04-21-2008 2:06 PM


Here's an interesting question that maybe someone here can answer. The question revolves around the fact that codons have associated anti-codons by way of charged tRNA (if my memory serves). I have been wondering about the 3 so-called stop codons, those codons that serve as a 'full stop' as it were. I understand that these 3 'stop codons' have no associated, or complimentary, anticodon/tRNA. Thus, when a ribosome encounters them (via mRNA), there are no more amino acids gathered and the amino acid chain breaks off etc. My question is: How come there is no anti-codon/tRNA complex for a stop codon? Are such potentially befitting tRNA's destroyed somehow, or is there some physiochemical reason why (just) these 3 particular anti-codons cannot form? Seems to me that, for life (as we know it), it is crucial to have a stop codon (like the importance of full stops in text). This means that it is either 'luck' that three codons do not have anti-codons or that there is some cellular mechanism to destroy them. The former might seem most plausible. But then again, why? Why shouldn't all codons have associated tRNA anti-codon complexes?
To further confuse the issue, there are apparently certain organisms in which the three stop-codons DO have anti-codons. Which supports the latter idea that there is a cellular mechanism to destroy any corresponding anti-codons for the stop codons. But then this begs the question as to how such a mechanism got started. Anyhow, I will be much obliged if anyone on this forum can shed light on this mystery. After all, I am assuming that the reason why stop codons do not have complimentary anti-codon tRNAs has been firmly established by geneticists.

Replies to this message:
 Message 3 by Blue Jay, posted 04-21-2008 3:33 PM semilanceata has replied
 Message 8 by Brad McFall, posted 04-21-2008 8:06 PM semilanceata has not replied
 Message 10 by kalimero, posted 04-22-2008 9:37 AM semilanceata has not replied
 Message 12 by Ooook!, posted 04-26-2008 8:39 AM semilanceata has replied

  
semilanceata
Junior Member (Idle past 5288 days)
Posts: 12
Joined: 04-21-2008


Message 4 of 14 (463871)
04-21-2008 3:43 PM
Reply to: Message 3 by Blue Jay
04-21-2008 3:33 PM


Are you saying that the reason there are not these 3 particular anti-codon/tRNAs is because there are no genes for making them? If so, I will have to dwell on this and get back to you if my mind still cannot settle on the issue.

This message is a reply to:
 Message 3 by Blue Jay, posted 04-21-2008 3:33 PM Blue Jay has not replied

Replies to this message:
 Message 5 by Dr Jack, posted 04-21-2008 5:45 PM semilanceata has not replied

  
semilanceata
Junior Member (Idle past 5288 days)
Posts: 12
Joined: 04-21-2008


Message 13 of 14 (464684)
04-28-2008 8:49 AM
Reply to: Message 12 by Ooook!
04-26-2008 8:39 AM


Re: What came first the tRNA or the Stop?
I have to confess that since posting the question, I am still baffled - in fact, the more I dwell on these matters the more perplexing it becomes. However, it seems the main answer is that charged tRNA's are specified by genes - and that there is no gene specifying STOP anti-codons (or such a gene is suppressed). Which, I suppose, makes sense. But then can a genetic system work without stop codons? I don't see how it could - because proteins are, apparently, quite specific in terms of their constituent amino acid chains. I would have thought that an in-effect 'stop command' was vital in specific protein building. So maybe, as you say, the original default situation was that all codons were STOP ones since charged tRNA genes had yet to evolve..... I dunno. Nature's 'technology' is extremely baffling. And quite brilliant too of course.

This message is a reply to:
 Message 12 by Ooook!, posted 04-26-2008 8:39 AM Ooook! has not replied

Replies to this message:
 Message 14 by molbiogirl, posted 04-29-2008 12:05 AM semilanceata has not replied

  
Newer Topic | Older Topic
Jump to:


Copyright 2001-2023 by EvC Forum, All Rights Reserved

™ Version 4.2
Innovative software from Qwixotic © 2024