The role of the G₁ period in the life cycle of eukaryotic cells

Abstract

The objective of this study was to test the concept that the G1 period lacks any specific function in the life cycle of mammalian cells and hence could be drastically reduced without any effect on the generation time. HeLa cells were grown in medium containing an optimum dose (60 microM) of hydroxyurea at which the duration of S period was prolonged with little or no increase in generation time. At this concentration of hydroxyurea, we observed a maximum of 3 h (or 28.5%) reduction in the G1 period. We also studied the effects of synchronization in S phase by single and double thymidine blocks on cell size and its relationship to the duration of G1 in the subsequent cycle. By these treatments, we could reduce the G1 period by not more than 2 to 3 h. The reduction in G1 period was not directly proportional to the size (volume) of the G1 cells. These results suggest that G1 period has certain specific functions and cannot be eliminated by alterations in culture conditions.

Cell proliferation in Allium cepa L. meristems under 8-hydroxyquinoline, a chelating agent that affects DNA and RNA polymerases

“…Furthermore, there must be some G 2specific functions in the plant DNA-division cycle, so that G 2 cannot be completely dispensed with, for G 2 was shortened up to 70 % of its control duration, but no more. The indispensability of a G 2 phase has been suggested for animal (Rao Satya-Prakash & Wang, 1984) and plant cells (Navarrete et al 1983).…”

Γονιδιακη Εκφραση Διεγερμενων Ανθρωπινων Τ-Λεμφοκυτταρων: Ρυθμιση Της Εκφρασης Του Γονιδιου 2 Κατα Τη Διαρκεια Του Κυτταρικου Κυκλου

“…Σημανχι,κό πλεονέκχημα χης μεθόδου συγκρίχυκά με άλλες μεθόδους κυχχαροκίνηχι,κής εύναι. η δυναχόχηχα προσδι.ορΐ-σμού χης ακριβούς θέσης ενός κυχχάρου μέσα σχη φάση Gl (Hittelman andRao 1976, 1978a) δεδομένου ÓXL λει.χουργι.κά σχάδι,α χης φάσης αυχής εύναί καθορι,σχι,κής σημασύας γυα χην πορεύα χου κυχχάρου μέσα σχον κυχχαρι,κό κύκλο (Rao et al, 1984. Tua xo λόγο αυχό η χεχνι,κή χης ΠΧΣ έχει.…”