Major subjects of DNA biophysics are briefly considered. Simplified
models are introduced, which are used to quantitatively understand
various properties of DNA. Special emphasis is made on the elastic-rod
model, which is used to describe DNA as a polymer molecule. Because
the DNA molecule often exists in a circular form, topology plays
a very important role in DNA. Two levels of DNA topology are considered,
knots and supercoils. Theoretical approaches to treat DNA topology
are described. Unusual DNA structures that are formed under high
negative supercoiling are introduced. A problem of specificity
of DNA negative supercoiling are introduced. A problem of specificity
of DNA interactions is formulated and discussed.
A preprint will be handed out at the lecture on June 26th.