At a broad level, all cancers have a defect in:
A DNA replication machinery
B the formation of mitochondria
C the cell’s ability to extract energy from nutrients
D cell cycle control
The correct answer and explanation is:
The correct answer is D) cell cycle control.
At a broad level, all cancers are characterized by defects in the normal regulation of the cell cycle. The cell cycle is a process through which a cell progresses from one division to the next, including stages such as growth (G1), DNA synthesis (S), preparation for division (G2), and actual division (M). These stages are tightly regulated by checkpoints that ensure the cell only progresses if certain conditions are met, such as accurate DNA replication and the proper alignment of chromosomes during mitosis.
In cancer, mutations in genes that regulate these checkpoints lead to uncontrolled cell division. These genes include oncogenes, which promote cell division when active, and tumor suppressor genes, which normally inhibit cell division or trigger apoptosis (programmed cell death) if the cell is damaged. When these genes are mutated, cells can bypass the checkpoints and continue dividing even when they should not. This results in the accumulation of genetic mutations and an uncontrolled growth of cells, forming tumors.
Additionally, cancer cells often exhibit altered signaling pathways, enabling them to evade growth suppressors and resist cell death signals. For example, mutations in the p53 gene, which is a tumor suppressor, are common in many cancers and contribute to the failure of cell cycle control.
While defects in DNA replication machinery, mitochondrial function, or energy extraction can also contribute to cancer, the central issue in the majority of cancer types is the disruption of the mechanisms that control when and how cells divide. This uncontrolled cell proliferation is the hallmark of cancerous growth.