  We have simulated structure and dynamics of water in the grooves of a DNA
duplex using moleculear dynamics simulations. We find signatures of a dynamical
transition in both translational and orientational dynamics of water molecules
in both the major and the minor grooves of a DNA duplex. The transition occurs
at a slightly higher temperature ($T_{GL} \approx $ 255 K) than the temperature
($T_L\approx$ 247 K) where the bulk water is conjectured to undergo a dynamical
transition. Groove water, however, exhibits markedly different temperature
dependence of its properties from the bulk. Entropy calculations reveal that
the minor groove water is ordered even at room temperature and the transition
at $T \approx$ 255 K can be characterized as a {\em strong-to-strong} dynamical
transition. The low temperature water is characterized by pronounced
tetrahedral order, as manifested in the sharp rise near $109^{\circ}$ in the
O-O-O angle distribution. We find that Adams-Gibbs relation between
configurational entropy and translational diffusion holds quite well when the
two quantities are plotted together in a master plot for different region of
aqueous DNA duplex (bulk, major and minor grooves) at different temperatures.
The activation energy for the transfer of water molecules between different
regions of DNA is found to be independent of temperature.
