Chargaff's bases

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ssas
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about chargaff's rule

Post by ssas » Tue Aug 15, 2006 2:55 pm

I don't think it can really happen like what Victor proposed.
Because it might ruin the whole structure of the 2 strands.
Deletion may happen but should rid bases of the both strands to maintain complementary pairing structure.
Am I right? please comment.
Anyway, what he said was quite impressive.

sdekivit
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Re: about chargaff's rule

Post by sdekivit » Tue Aug 15, 2006 3:19 pm

ssas wrote:I don't think it can really happen like what Victor proposed.
Because it might ruin the whole structure of the 2 strands.
Deletion may happen but should rid bases of the both strands to maintain complementary pairing structure.
Am I right? please comment.
Anyway, what he said was quite impressive.


Because of tautomerism an A can form a rare imino tautomer which can bind to C which is stable and occurs in DNA.

Tautomerism occurs 1 to 10^4 bases. During incorporation a C can be bound to the A*, when A is in the imino form. During the next replication it can retautomerize to the normal A and than a T is incorporated, but on the other strand, because a C was bound, the A is replaced by a G.

This is complex chemistry though. The same can happen when the mutagen 5-bromouracil is precent. Normally U will bind A, but 5-bromouracil i=can tautomerize to a so-called enol form which has a higher frequence. It binds a G instead of A. Therefore during the next replication instead of an AT-couple a CG-couple is made.

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Post by ssas » Wed Aug 16, 2006 1:26 am

Yes, mismatch might occur occasionally, but should not happen all through the strands continuously, right?

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Post by sdekivit » Wed Aug 16, 2006 7:27 am

no, its approximately 1 : 10^4. Thus 1 mismatch in 10^4 bases.

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