Checkpoint control

Definition

Checkpoint control refers to a regulatory mechanism in the cell cycle that ensures the proper progression of cell division and prevents cells from undergoing division when certain conditions are not met. These checkpoints serve as critical decision points where the cell assesses its internal and external environment, such as DNA integrity, nutrient availability, and cell size, before allowing the cell to proceed to the next stage of division. If issues are detected, checkpoint control can halt the cell cycle, allowing time for repair or triggering programmed cell death.

5 Must Know Facts For Your Next Test

1. Checkpoints exist at several stages of the cell cycle, primarily at G1, G2, and M phases, each serving different functions in monitoring the cell's readiness for division.
2. The G1 checkpoint checks for DNA damage and ensures that the cell is large enough and has sufficient nutrients before committing to DNA replication.
3. The G2 checkpoint verifies that DNA replication has occurred without error and prepares the cell for mitosis by checking for damage and ensuring all necessary proteins are present.
4. The M checkpoint occurs during metaphase and ensures that all chromosomes are properly attached to the spindle apparatus before proceeding to anaphase.
5. Defects in checkpoint control can lead to genomic instability and contribute to tumorigenesis by allowing cells with damaged DNA to continue dividing.

Review Questions

• How do checkpoint controls contribute to preventing cancer development?
  • Checkpoint controls play a crucial role in preventing cancer by monitoring key processes during the cell cycle. They ensure that cells do not proceed to divide when there are signs of DNA damage or other abnormalities. By halting the cycle for repairs or triggering apoptosis if repair is impossible, these checkpoints help maintain genomic stability and prevent the propagation of potentially cancerous cells.
• What is the relationship between tumor suppressor genes and checkpoint control mechanisms?
  • Tumor suppressor genes are integral to checkpoint control mechanisms as they produce proteins that regulate the cell cycle and promote DNA repair. When functioning correctly, these proteins can detect problems within the cell and initiate necessary halting of division at checkpoints. However, mutations in tumor suppressor genes can impair this ability, leading to loss of control over cell proliferation and increased risk of cancer.
• Evaluate how mutations in proto-oncogenes can affect checkpoint control and contribute to tumorigenesis.
  • Mutations in proto-oncogenes can lead to their transformation into oncogenes, which may produce proteins that promote excessive cell division or override normal checkpoint controls. This unchecked growth can disrupt the delicate balance maintained by checkpoint mechanisms, allowing cells with damaged DNA or other issues to continue dividing. As a result, these mutations contribute significantly to tumorigenesis by fostering an environment where cancerous cells can thrive unchecked.

Related terms

Tumor Suppressor Genes: Genes that produce proteins responsible for regulating cell division and ensuring cells do not grow uncontrollably. Mutations in these genes can lead to cancer.

Proto-oncogenes: Normal genes that help regulate cell growth and division. When mutated, they can become oncogenes, promoting uncontrolled cell proliferation.

Apoptosis: A form of programmed cell death that allows organisms to eliminate damaged or unwanted cells in a controlled manner, preventing cancerous growth.