OldOld A G G G New G G G Old New New Old Figure 13.1 The original Watson-Crick proposal for the replication of a double-helical molecule of DNA.During replication,the double helix unwinds,and each of the parental strands serves as a template for the synthesis of a new complementary strand.As discussed at length in this chapter,the basic tenets of this proposal have been borne out
DNA复制和细胞周期的关系： ◼ DNA复制是细胞周期的决定因素， DNA复制完成以前，细胞不会发生分 裂。 ◼ DNA复制的完成是细胞分裂的触发点， 复制后的基因组被平均分配到两个子 细胞中去。细胞周期调控基因控制 DNA的复制并触发细胞分裂
DNA复制和细胞周期的关系： ◼ DNA复制是细胞周期的决定因素， DNA复制完成以前，细胞不会发生分 裂。 ◼ DNA复制的完成是细胞分裂的触发点， 复制后的基因组被平均分配到两个子 细胞中去。细胞周期调控基因控制 DNA的复制并触发细胞分裂
Go phase reactivation 88 Go phase indefinite withdrawal 1h M G2 phase 3-4h 4n DNA G1 phase 6-12h S phase 2n DNA 6-8h DNA synthesis 2-4n DNA
G1 phase S phase G2 phase Mass Protein 32 RNA 16 8 DNA 2 0 8 16 24 hours
G1 G2 Basic cycle control ↑↑ Mitosis START/ DNA synthesis DNA synthesis Mitosis Mitosis ends Restriction point starts ends starts ends ■ ◆ ■ ■ ■ ◆ ■ ◆ Check- point ■ ◆ controls ◆ ■ ■■■■■■■■ Checkpoint Checkpoints Checkpoints Checkpoint for division for DNA integrity for unreplicated DNA for paired kinetochores