  The most important features of the pseudo SU(3) model are reviewed. This
description of heavy deformed nuclei is based on pseudo spin symmetry, and is
able to correctly predict the collective spectra and their transition
amplitudes, using appropriate effective charges. It also gives a very good
description of the exotic double beta decay, a hard test of any nuclear model.
The simplest pseudo SU(3) assumptions describe nucleons in the abnormal parity
states as having seniority zero. This idea is very useful as a mathematical
simplification, and is also able to give a nice description of the backbending
phenomena, but has been challenged in a recent study about effective charges
and $BE2(0^+_1 \rightarrow 2^+_1)$ systematics. We carefully checked this
statement and conclude that the seniority zero approach is a formal way of
assign abnormal parity nucleons a passive role. The contribution of the
abnormal parity nucleons to the nuclear quadrupole moments is finite but only a
fraction of their asymptotic Nilsson values.
