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Author Topic:   Wright et al. on the Process of Mutation
Dr Jack
Member (Idle past 969 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 5 of 296 (627346)
08-02-2011 6:18 AM
Reply to: Message 1 by Taq
08-01-2011 6:23 PM


Their claim is not well supported.
quote:
This article presents evidence that starvation for leucine in an Escherichia coli auxotroph triggers metabolic activities that specifically target the leu operon for derepression, increased rates of transcription, and mutation.

That seems a monumentally unsupported claim. It seems to me that their results are better explained in two ways, one of which is discussed in their own discussion section and one of which isn't.

1. As discussed in their discussion and supported by other papers: transcription increases the chances of mutation. This should surprise no-one: DNA is usually packaged in a manner to ensure its protection and only unravelled when copied or expressed.

2. As not discussed in the paper. A mutant that is already derepressed will experience a significant selective advantage when it is put into the starvation conditions as it will already have the required enzymes in place; this means a sample taken post-starvation will have a vastly increased chance of finding a bacterium that is descended from a pre-starvation mutant. I see nothing in their method that would distinguish between a pre-starvation mutant and one that occurred during starvation.


This message is a reply to:
 Message 1 by Taq, posted 08-01-2011 6:23 PM Taq has responded

Replies to this message:
 Message 7 by Taq, posted 08-02-2011 11:32 AM Dr Jack has responded

  
Dr Jack
Member (Idle past 969 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 8 of 296 (627414)
08-02-2011 12:16 PM
Reply to: Message 7 by Taq
08-02-2011 11:32 AM


Re: Their claim is not well supported.
I'm remain unconvinced. The mutation rate is never going to be zero.

This message is a reply to:
 Message 7 by Taq, posted 08-02-2011 11:32 AM Taq has responded

Replies to this message:
 Message 9 by Taq, posted 08-02-2011 9:35 PM Dr Jack has responded

  
Dr Jack
Member (Idle past 969 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 11 of 296 (627636)
08-03-2011 4:56 AM
Reply to: Message 9 by Taq
08-02-2011 9:35 PM


Re: Their claim is not well supported.
I don't see how what they've done rules out a selection effect, especially as they haven't worked out the prevalence of the mutation in the basal population.

This message is a reply to:
 Message 9 by Taq, posted 08-02-2011 9:35 PM Taq has not yet responded

Replies to this message:
 Message 12 by Wounded King, posted 08-03-2011 6:31 AM Dr Jack has not yet responded

  
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