The duration of the premeiotic DNA synthesis in mouse oocytes

The premeiotic DNA replication of euchromatin and heterochromatin in Lilium longiflorum (Thunb.)

“…Biochemical studies have revealed that only 0.3 % of the DNA remains unreplicated during leptotene (29,32) and that this DNA is replicated during zygotene. Studies of other organisms have likewise shown a termination of DNA replication prior to leptotene (17,39,46) or even before zygotene 03, 18).…”

“…Moreover it is possible to calculate the time difference between these individual gradients using the mean lengths of buds housing two sequential types of gradients and the observed growth rate of 7 %/24 hours. The resul[s presented in Table I demonstrate that the established sequence of developmental gradients is valid, the individual gradients being separated in time by [16][17][18][19][20] hours. Since the developmental difference between the anther gradients is 2/3 of the base-tip difference, the mean time difference between the stages housed in the tip and the base of the anthers is 24-30 hours.…”

“…Culture experiments of extruded microsporocytes have demonstrated that the cells become irreversibly committed t ~ meiosis during the premeiotic interphase (54,63). The premeiotic DNA replication has been reported to be longer than somatic DNA replication (55,64) a characteristic found in all organisms investigated (3,17,19,50) and in particular in the newt Triturus (11,12,13). The major phase of premeiotic DNA replication terminates at the onset of leptotene (29,32,71) but biochemical analyses have demonstrated that 0.3 % of the DNA in Lilium is delayed in replication until zygotene (29,32).…”

“…This increase by a factor 6 is in good agreement with the results from Triturus where the premeiotic and somatic S phases lasted 9-10 and 2 days respectively (11,13). In Triticum and in the mouse the premeiotic DNA replication has been estimated to take twice as long as the somatic replication (3,17).…”

Autoradiographic studies on the chronology of meiosis and spermiogenesis in the cat.

“…Unlike females, the meiosis in males starts postnatally and is a continuous process of rather shorter duration. Moreover, a postmeiotic DNA synthesis gap, comparable to the G, period of somatic cells (Mukherjee et al 1968) and oocytes (Crone et al 1965), has never been reported in mammalian spermatocytes (Roosen-Runge 1977, Ghosal et al 1983. During the course of the present investigation labelled leptotenes were scored as early as 1 hour (0.04d) following the administration of tritiated thymidine.…”