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Oncogenes and Tumor Suppressors quiz #1

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  • How do oncogenes influence the cell cycle in cancer cells?
    Oncogenes, when mutated and overexpressed, promote cell proliferation and survival by stimulating growth signals and cell cycle progression, leading to uncontrolled cell division and tumor development.
  • What is the effect of losing p53 activity in a cell?
    Loss of p53 activity prevents the cell from responding to DNA damage, allowing mutations to accumulate and enabling cells to divide unchecked, which promotes tumor growth and genetic instability.
  • Why does the loss of p53 activity contribute to cancer development?
    Without functional p53, cells cannot initiate DNA repair or apoptosis in response to DNA damage, resulting in the survival and proliferation of genetically unstable cells that can form tumors.
  • What property allows cancer cells to grow without external growth signals?
    Cancer cells acquire mutations that enable them to proliferate independently of external growth signals. This contributes to uncontrolled cell division and tumor formation.
  • How does gene amplification contribute to oncogene overexpression?
    Gene amplification results in multiple copies of an oncogene, leading to increased expression of its protein product. This heightened activity can drive cell proliferation and cancer development.
  • What is the role of angiogenesis in tumor survival?
    Angiogenesis allows tumors to stimulate the growth of new blood vessels, providing essential nutrients and oxygen. This process supports continued tumor growth and survival.
  • Why is RAS considered a significant oncogene in human cancers?
    RAS is a GTPase that, when mutated, is overexpressed and activates multiple signaling pathways. It is implicated in about 20% of all human cancers due to its central role in cell proliferation.
  • What happens when retinoblastoma tumor suppressor is mutated?
    Mutation of the retinoblastoma gene leads to loss of cell cycle regulation, allowing uncontrolled cell division. This mutation can sometimes be inherited if present in germ cells.
  • How do cancer cells evade apoptosis despite receiving death signals?
    Mutations in cancer cells allow them to ignore apoptosis signals, enabling them to survive and proliferate. This evasion is a key factor in tumor growth and resistance to therapy.
  • What is the consequence of genetic instability in cancer cells?
    Genetic instability causes cancer cells to accumulate mutations at a rapid rate. This leads to increased diversity within tumors and can promote progression and resistance to treatment.