A-DNA and Z-DNA Atlases. Dave Ussery Comparative Microbial Genomics first lecture, 18 September, 2002. Outline. Helix family. A-DNA. A-DNA helix. A-DNA was the first DNA helix characterised by Rosalind Franklin in the early 1950’s. A-DNA helices
Comparative Microbial Genomics
first lecture, 18 September, 2002
Z-DNA was the first DNA helix to be crystallised
(in 1979), and came to the surprise of many biologists.
It is a thin, LEFT-HANDED helix, with 12 bp/turn,
and has a zig-zag backbone (hence its name). Certain
alternating pyrimidine/purine sequences
(e.g., CGCGCG) will form this helix.
Consider a stretch of purines (G or A, abbreviated R)
of length n:
What is the probability of finding this in a random DNA