Biology · MU Pleven

26.Cell cycle. Control of the cell cycle. Individual development of the cells.

Covers the phases of the cell cycle, from interphase with its G1, S and G2 stages to the mitotic phase, including karyokinesis, cytokinesis and the two types of mitosis. Explains the G0 state, the major checkpoints and how cyclins and cyclin-dependent kinases regulate progression through the cycle.

Inside: 6 sections · 3 labelled pictures · 14 flashcards · 3 min

Topic 26 of 63 in the MU Pleven syllabus for Biology (Medicine, Year 1). The free AceMed note covers it in 6 sections, about 354 words (3 min of reading), with 14 flashcards.

In this note

  1. Cell cycle. Control of the cell cycle. Individual development of the cells.
  2. Cell Cycle and Individual Cell Development
  3. G0 Phase
  4. Interphase
  5. Mitotic (M) Phase
  6. Regulation of the Cell Cycle

Cell Cycle and Individual Cell Development

The cell cycle is the sequence of events a cell undergoes to grow, replicate DNA, and divide into two daughter cells. In eukaryotes, it is divided into interphase, the mitotic (M) phase, and cytokinesis. Interphase is for growth and DNA replication, the mitotic phase separates chromosomes, and cytokinesis completes cell division. Checkpoints ensure proper progression of the cycle.

The cell cycle is vital for development, tissue renewal (e.g., skin, hair, blood), and organismal growth. After division, daughter cells enter interphase to begin a new cycle. Each phase involves specialized biochemical processes that prepare the cell for division.

G0 Phase

  • Known as the post-mitotic phase, cells in G0 are non-dividing, either quiescent or senescent.
  • Fully differentiated cells (e.g., neurons) may remain in G0 indefinitely.
  • Senescence prevents damaged DNA from producing nonviable or cancerous progeny.
  • Some cells (e.g., liver, kidney) enter G0 semi-permanently, while others (e.g., epithelial cells) keep dividing.

Interphase

  • The preparatory phase before division, previously called the resting stage.
  • Prepares the cell by nutrient accumulation and DNA replication.
  • Occupies ~90% of the cell cycle.
  • Stages of Interphase:
  • G1 phase (growth): High biosynthetic activity, organelle duplication, cell enlargement.
  • S phase (synthesis): DNA replication occurs; each chromosome forms sister chromatids, doubling DNA amount.
  • G2 phase: Prepares for mitosis with additional proteins and organelles.

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