The effects of imprinting

The effects of imprinting can be observed at several levels:
that of the whole genome, that of particular chromosomes or
chromosomal segments, and that of individual genes. For
example, the effect of triploidy in human conceptions depends
on the origin of the additional haploid chromosome set. When
paternally derived, the placenta is large and cystic with molar
changes and the fetus has a large head and small body. When
the extra chromosome set is maternal, the placenta is small and
underdeveloped without cystic changes and the fetus is
noticeably underdeveloped. An analogous situation is seen in
conceptions with only a maternal or paternal genetic
contribution. Androgenic conceptions, arising by replacement
of the female pronucleus with a second male pronucleus, give
rise to hydatidiform moles which lack embryonic tissues.
Gynogenetic conceptions, arising by replacement of the male
pronucleus with a second female one, results in dermoid cysts
that develop into multitissue ovarian teratomas.