  We introduce a spatially explicit model for the competition between type $a$
and type $b$ alleles. Each vertex of the $d$-dimensional integer lattice is
occupied by a diploid individual, which is in one of three possible states or
genotypes: $aa$, $ab$ or $bb$. We are interested in the long-term behavior of
the gene frequencies when Mendel's law of segregation does not hold. This
results in a voter type model depending on four parameters; each of these
parameters measures the strength of competition between genes during meiosis.
We prove that with or without a spatial structure, type $a$ and type $b$
alleles coexist at equilibrium when homozygotes are poor competitors. The
inclusion of a spatial structure, however, reduces the parameter region where
coexistence occurs.
