2- tumour suppressor and oncogenes Flashcards
What are the two main types of genetic mutations that can cause cancer?
Cancer can result from mutations involving tumor suppressor genes or the creation of oncogenes.
Define tumor suppressor genes and their role in preventing cancer.
Tumor suppressor genes protect against DNA disruption and mutations. They play a role in maintaining genomic stability and preventing the development of tumors.
Explain the role of the type II alveolar cells in lung cancer development.
Type II alveolar cells, with a healthy genetic code, may become cancerous due to exposure to carcinogens, such as those in cigarette smoke. Carcinogens can lead to DNA mutations and increase the likelihood of developing cancer.
Describe the function of the TP53 gene and its protein product, p53.
TP53 codes for the p53 protein, known as the guardian of the genome. It is involved in DNA repair, cell cycle regulation, and apoptosis. Mutations in TP53 are found in many solid tumors, making it an early mutation in cancer development
How do oncogenes contribute to cancer development, and provide an example.
Oncogenes are new genes that promote abnormal cell growth. An example is the BCR-ABL fusion oncogene, which results from the fusion of the BCR gene on chromosome 9 with the ABL gene on chromosome 22, leading to uncontrolled cell division.
What were the two opposing theories in the early 20th century regarding the causes of cancer?
The two theories were that cancer is caused by chemicals (carcinogens) or by infectious agents.
Explain the role of Rous sarcoma virus (RSV) in cancer research.
RSV, a retrovirus, was crucial in the discovery of oncogenes. The v-src gene in RSV was identified as an oncogene, showing that viruses could carry genes capable of inducing cell transformation.
What is the significance of chromosomal rearrangements in creating oncogenes?
Chromosomal rearrangements, such as reciprocal translocations, can upregulate proto-oncogenes, leading to the creation of oncogenes. An example is the myc oncogene, which, when fused with the IgH promoter region, causes cancer.
Explain the concept of Loss of Heterozygosity (LOH) and its role in hereditary cancers.
LOH occurs when one allele of a gene is lost, typically due to mitotic recombination. It explains how both copies of the RB gene can be eliminated during the formation of hereditary retinoblastomas.
Differentiate between gatekeeper and caretaker tumor suppressors, providing examples.
Gatekeeper tumor suppressors control cell proliferation, while caretaker tumor suppressors ensure genome stability. Examples of caretaker tumor suppressors include BRCA1/2, which are often lost in breast cancers.
What does Peto’s paradox reveal about cancer susceptibility?
Peto’s paradox challenges the expectation that larger animals with more cells, like whales or elephants, would have a higher cancer risk. The paradox suggests that species with more effective tumor suppressor mechanisms, such as p53, may have lower cancer susceptibility.
Describe the Ames test and its significance in linking carcinogens and mutagenicity.
The Ames test, developed by Bruce Ames, uses a specific strain of Salmonella to quantify mutagenicity. It provided robust evidence that carcinogens are mutagens, establishing a correlation between mutagenicity and carcinogenicity.
