Infertility as opposed to inviability appears to be the most normal sex-skewed outcome, as
heterogametic infertility is known to outnumber
heterogametic inviability about 10:1 in Drosophila and mammals (Wu and Davis 1993).
Mims, "Evidence for female
heterogametic sex determination in paddlefish Polyodon spathula based on gynogenesis," Aquaculture, vol.
Females are
heterogametic (Z0 or WZ) and males are homogametic (ZZ), although sporadic rearrangements created multiple sex chromosome systems in some species (Traut et al.
In birds, females are the
heterogametic sex (ZZ/ZW system).
Sexual differentiation in dioecious strains is based on a pair of sex chromosomes, the male being
heterogametic (XY, the Y chromosome allegedly larger (Sakamoto et al., 1998), unlike mammals, but like some other plants), producing an approximately 50:50 sex ratio.
Previous studies on fluted pumpkin reported an XY system of sex chromosomes with homogametic XX female and
heterogametic XY male [6].
In a minority of dioecious plants, sex determination depends on sex chromosomes, usually an XY system, in which males are
heterogametic (XY) and females are homogametic (XX) [1-3].
In mammals, the
heterogametic male XY system uses SRY, a sex-determining gene on the Y chromosome (SRY) to initiate the male pathway.
Higher possible genomic mortality of
heterogametic (ZW) females compared with homogametic males (ZZ) allows the males of these species to offer sacrifice to save the females, which has the responsibility of rearing the brood.
mori, are designated ZW for the
heterogametic female and ZZ for the homogametic male (Yokoyama et al., 2003; Nagaraju, 1996).
In birds, females are the
heterogametic sex (ZW) and males are homogametic (ZZ) (Ellegren 1996).