10.5: 间期

细胞周期发生在大约24小时（在一个典型的人类细胞中）和两个不同的阶段：间期，包括细胞周期的三个阶段（g₁、s和g₂）和有丝分裂（m）。在占真核细胞周期95%的间期，细胞在有丝分裂前生长并复制其DNA。

相间阶段

在有丝分裂和胞质分裂的每个阶段之后，真核细胞进入间期，在此期间它们生长并复制其DNA，为下一次有丝分裂做准备。

在G1 (gap 1) 阶段，细胞持续生长并准备DNA复制。在此阶段，细胞代谢活跃，复制重要的细胞器和生化分子，如蛋白质。

在随后的S （合成）期间期，细胞复制其细胞核DNA，并将其包装在半浓缩染色质中。在s期，细胞也复制中心体，一种形成有丝分裂纺锤体的微管组织结构。有丝分裂纺锤体在有丝分裂期间分离染色体。

在DNA合成之后的G2 (gap 2) 阶段，细胞继续生长并合成蛋白质和细胞器，为有丝分裂做准备。

在人细胞中，G1期约11小时，S期约8小时，G2期约4小时。在G1期间，细胞是二倍体（2n，每个染色体一对）。在S期复制后，细胞的DNA含量增加到4n，细胞保持4n直到胞质分裂，此时DNA含量减少到2n。

在真核细胞中

细胞周期的最长的部分是分裂间期

它分为三个阶段G1 S和G2

G1 第一个间隙期

新生成的子细胞大小增加

并下一阶段DNA复制做准备

S期 合成期

细胞复制核DNA

仍然包装为染色质

细胞还复制中心体

即微管组织结构

其形成有丝分裂纺锤体

最终 G2 第二个间隙期

细胞继续生长 繁殖细胞器

和有丝分裂所需的蛋白质

并补充其能量储备

细胞现在已准备好进入有丝分裂的第一阶段

• Cell Cycle – Series of stages a cell undergoes to grow, replicate DNA, and divide into two daughter cells.
• Interphase – Longest cell cycle phase where cells grow, replicate DNA, and prepare for mitosis.
• G1 Phase – First growth phase marked by active metabolism and organelle duplication.
• S Phase – Phase when DNA is replicated and centrosomes are duplicated for cell division.
• G2 Phase – Final interphase stage with continued growth and protein synthesis before mitosis.

• Define Interphase Phases – Recognize the G1, S, and G2 stages where cells grow, replicate DNA, and prepare for mitosis (e.g., cell cycle).
• Understand DNA Replication – Learn how DNA strands are duplicated during the S phase using semiconservative synthesis (e.g., synthesis).
• Track Cell Growth – Identify key processes in G1 and G2 like organelle duplication and protein synthesis before mitosis (e.g., growth).
• Compare DNA Content – Follow chromosome duplication from diploid (2n) to tetraploid (4n) and return to 2n after cytokinesis.
• Prepare for Mitosis – Understand interphase as a foundation for cell division.

• What is interphase in the cell cycle and why is it essential for cell division?
• What happens in the S phase of the interphase and why is DNA replication important?
• What happens during the G2 phase of interphase and how does it prepare the cell for mitosis?

• Students – Understand what happens during interphase and why it is essential in the cell cycle.
• Educators – Provides a clear framework for teaching the stages of interphase (G1, S, and G2) and their role in cell division.
• Researchers – Reinforces the importance of interphase in preparing cells for mitosis or meiosis.
• Science Enthusiasts – Offers insights into how cells grow, duplicate DNA, and preserve genetic stability before dividing.