S phase

Definition

The S phase, or synthesis phase, is a key part of the cell cycle where DNA replication occurs, allowing a cell to double its genetic material before division. This phase is critical for ensuring that each daughter cell receives an identical set of chromosomes, maintaining genetic consistency and integrity across generations of cells.

5 Must Know Facts For Your Next Test

1. The S phase is preceded by the G1 phase and followed by the G2 phase in interphase.
2. During the S phase, each chromosome is replicated to produce two sister chromatids, ensuring proper distribution during cell division.
3. The accuracy of DNA replication during the S phase is crucial; errors can lead to mutations or chromosomal abnormalities.
4. Regulatory proteins and checkpoints monitor the integrity of DNA during the S phase to prevent progression if issues are detected.
5. The duration of the S phase can vary between different cell types; rapidly dividing cells have a shorter S phase compared to those that divide infrequently.

Review Questions

• How does the S phase contribute to the overall process of the cell cycle?
  • The S phase plays a crucial role in the cell cycle as it is when DNA replication occurs. This ensures that each daughter cell receives a complete set of chromosomes, which is essential for maintaining genetic stability. Without the S phase, cells would not be able to properly prepare for division, leading to potential issues such as incomplete genetic information in daughter cells.
• Discuss how checkpoints during the S phase help maintain genomic stability.
  • Checkpoints during the S phase serve as critical regulatory points that monitor DNA integrity and ensure that replication proceeds accurately. If any damage or errors are detected in the DNA, these checkpoints can halt the progression into later stages of the cell cycle until repairs are made. This process helps prevent the transmission of mutations to daughter cells, thus maintaining genomic stability.
• Evaluate the implications of errors occurring during the S phase on cellular function and organismal health.
  • Errors occurring during the S phase can lead to mutations in the replicated DNA, which may result in dysfunctional proteins or disrupted cellular processes. Such mutations can contribute to diseases like cancer if they affect genes responsible for regulating cell growth and division. Additionally, accumulated mutations over time can lead to significant organismal health issues, highlighting the importance of accurate DNA replication during this critical phase of the cell cycle.

Related terms

Interphase: The stage of the cell cycle that includes G1, S, and G2 phases, during which the cell prepares for division.

DNA Replication: The process by which a cell makes an exact copy of its DNA before it divides.

G1 Phase: The first gap phase in the cell cycle where the cell grows and prepares for DNA synthesis.