A reassessment is made of some results for linear and circular DNA. Th
e alternative side-by-side configuration is used in an analysis of sit
uations where some doubt about current double helix based interpretati
ons may exist. The following specific areas are considered: (i) certai
n linear DNA examples involving duplex interactions, (ii) nucleosome s
equence data and (iii) the banding effect observed in gel electrophore
sis studies of in vitro circular DNA.