  A small quantum dot coupled to two external leads is considered. Different
signs of the dot-leads coupling matrix elements give rise to qualitatively
different behavior of physical observables such as the conductance, the phase
of the transmission amplitude and the differential capacitance of the dot. For
certain relative signs the conductance may vanish at values of the gate
potential, where the spectral density is maximal. Zeroes of the conductance are
robust against increasing the dot-lead coupling. They are associated with
abrupt phase lapses in the transmission phase whose width vanishes as the
square of the temperature. We carefully distinguish between phase lapses of
$-\pi$ and phase anti-lapses of $\pi$.
