General Biology 1: Cell Cycle Phases

Cell Cycle Overview

• The cell cycle consists of two main phases: Interphase and M Phase (Mitosis).
• Interphase is divided into three further phases: G1, S, and G2.

Phases of Interphase

• G1 Phase:
  • Involves cell growth without DNA replication.
  • Cells prepare for DNA synthesis.
• S Phase:
  • DNA synthesis occurs, resulting in DNA doubling.
  • Essential for preparing genetic material for cell division.
• G2 Phase:
  • The cell synthesizes proteins and organelles in preparation for mitosis.

M Phase

• M Phase includes mitosis and cytokinesis, where the actual division of the cell occurs.

Duration of the Cell Cycle

• The typical duration of the cell cycle in human cells is approximately 24 hours.
• Interphase occupies more than 95% of the total cycle duration.

Quiescent Stage (G0)

• G0 is an active stage where cells remain metabolically active but do not proliferate, often entered by cells that are not currently dividing.

Importance of Cell Division

• Cell division is vital for reproduction, growth, and repair in living organisms.
• It plays a crucial role in multicellular organisms by facilitating tissue growth and regeneration.

Consequences of Skipping Cell Cycle Phases

• Skipping the S Phase may lead to daughter cells having incomplete genomes.
• Proper replication ensures that daughter cells inherit the correct amount of genetic material.

Control Points in the Cell Cycle

• The cell cycle is regulated by control points that ensure conditions are favorable for progression to the next phase.
• Checkpoints occur at key stages: G1, G2, and during mitosis to prevent errors.

Key Functions of DNA Replication

• DNA replication is critical for duplicating the genome prior to mitosis.
• It ensures that both daughter cells receive identical copies of the genetic material.