MadSci Network: Molecular Biology |
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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