  In many organisms, homologous (or repetitive) chromosomal regions can
associate or/and undergo concerted epigenetic changes in the absence of DNA
breakage and recombination. The direct specific pairing of DNA duplexes with
similar nucleotide sequences represents an attractive mechanism for recognizing
such regions. Whereas the pairing of B-DNA duplexes may involve a large energy
barrier, C-DNA duplexes are expected to pair much more readily. This unique
feature of C-DNA is largely due to the fact that its major groove is wide and
very shallow, permitting almost perfect initial homologous contacts between two
duplexes without clashing. Overall, the conjectured role of C-DNA in
recombination-independent pairing should revive the efforts to understand its
structure and function in the cell.
