MadSci Network: Molecular Biology
Query:

Re: What is the relationship between nucleotide sequence and DNA structure?

Date: Thu Feb 27 12:07:00 2003
Posted By: Sabine Heinhorst, Faculty, Chemistry and Biochemistry, The University of Southern Mississippi
Area of science: Molecular Biology
ID: 1045368823.Mb
Message:

Dear Trey,

At first glance, DNA structure is independent of nucleotide sequence, 
since the A=T and C=G base pairs have roughly the same dimensions. 
However, if one looks more closely, one does see that DNA structure 
differ 
depending on its nucleotide sequence. An example: a certain 
arrangement of 
tracts of adenosine residues in one strand can lead to the bending of the 
DNA.
For an overview of DNA bending, see  
http://access.ncsa.uiuc.edu/Stories/DNABending/DNABending.html.

A very unusual structural variation of “normal” (= B) DNA is Z DNA, named 
for the zig-zag pattern the ribose-phosphate backbone follows in this left-
handed double helix. Z-DNA formation is favored by alternating purine-
pyrimidine sequences, e.g. (CG)n.
For a more in-depth treatment of structural variations in DNA, see: 
http
://cmgm.stanford.edu/biochem201/Handouts/DNAStructures.pdf, and 
for 
some great slides, see: http://cmgm.stanford.edu/biochem201/Slides/DNA%
20Structure/

There are also some subtle changes in the tilt angles of the bases and 
their relative orientation to each other that depend on sequence context. 

Hope this answers your question.

Sincerely,

Sabine Heinhorst




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