  We obtain the finite-temperature unconditional master equation of the density
matrix for two coupled quantum dots (CQD) when one dot is subjected to a
measurement of its electron occupation number using a point contact (PC). To
determine how the CQD system state depends on the actual current through the PC
device, we use the so-called quantum trajectory method to derive the
zero-temperature conditional master equation. We first treat the electron
tunneling through the PC barrier as a classical stochastic point process (a
quantum-jump model). Then we show explicitly that our results can be extended
to the quantum-diffusive limit when the average electron tunneling rate is very
large compared to the extra change of the tunneling rate due to the presence of
the electron in the dot closer to the PC. We find that in both quantum-jump and
quantum-diffusive cases, the conditional dynamics of the CQD system can be
described by the stochastic Schr\"{o}dinger equations for its conditioned state
vector if and only if the information carried away from the CQD system by the
PC reservoirs can be recovered by the perfect detection of the measurements.
