  The denaturation of double-stranded DNA as function of force and temperature
is discussed. At room temperature, sequence heterogeneity dominates the physics
of single molecule force-extension curves starting about 7 piconewtons of below
a ~15 pN unzipping transition. The dynamics of the unzipping fork exhibits
anomalous drift and diffusion in a similar range above this transition. Energy
barriers near the transition scale as the square root of the genome size.
Recent observations of jumps and plateaus in the unzipping of lambda phage DNA
at constant force are consistent with these predictions.
