This low rate of incidence may have been unperceived by the Talmud Sages, or it may have been recognized as an anomaly, causing the Sages to disregard
biparental inheritance of genetic coagulation disorders as a significant halakhic factor.
In the vegetative cell of pollen grain, plastid DNA breaks down from pollen mitosis independently of maternal or biparental inheritance (Sodmergen et al., 1992).
Biparental inheritance is very rare in angiosperms and has been described in only a few species--namely, Medicago sativa (Schumann & Hancock, 1989; Corriveau et al., 1990), Daucus (Hause, 1991), Pelargonium zonale (Sodmergen et al., 1992, 1994, 1998), Rhododendron mucronatum (Nagata et al., 1999a), and Pharbitis nil (Nagata et al., 1999b)--without any report on the mechanism of plastid distribution during pollen development.
In species with biparental inheritance, however, plastid DNA is intensively synthesized during the end of pollen maturation (Miyamura et al., 1987), and DNA content is multiplied up to twelvefold (Nagata et al., 1999b).