An example of a tumour suppressor gene is-

Ans. is 'd' i.e., RB Tumor suppressor geneo The replication of cell should be controlled to maintain a steady state.o Failure to inhibit cell replication is one of the fundamental alterations in the process of carcinogenesis.o Tumor suppressor genes are the genes whose products down regulate the cell cycle and thus apply brakes to cellular proliferation.o So, loss of function of tumor suppressor genes results in uncontrolled cell proliferation and carcinogenesis,o Similar to oncogene, tumor suppresor gene may be -# Cell surface receptor # Transduction molecules # Transcription factorIn additiono Cell cycle inhibitorso Regulators of cellular responses to DNA damage (DNA repair regulators)These protein products are involved in -o Cell cycle controlo Regulation of apoptosiso DNA repairTUMOUR SUPPRESSOR GENESubcellular LocationTumor su pressor GeneFunctionTumors Associated with Somatic MutationsThmors Associated with inherited MutationCell surfaceo TGF-b receptoro Growth inhibitiono Carcinomas of colono Unknown o E - cadherino Cell adhesiono Carcinoma of stomacho Familial gastric cancerInner aspect of plasma membraneNF-lInhibition of RAS signal transduction and of p21 cell - cycle inhibitorNeuroblastomasNeurofibromatosis type I and sarcomasCytoskeletonNF-2Cytoskeletal stabilitySchwannomas and meningiomasNeurofibromatosis type - 2 acoustic schwannomas and meningiomasCytosolo APC/b-catenino Inhibition of signal transdu- ctiono Carcinomas of stomach, colon, pancreas; melanomao Familial adenomatous polyposis coli/colon cancer o PTENo PI - 3 kinase signal transductiono Endometrial and prostate cancerso Unknown o SMAD 2 and SMAD4o TFG - b signal transductiona Colon, pancreas tumorso UnknownNucleuso RBo Regulation of cel l cycleo Retinoblastoma: osteosarcoma carcinoma of breast, colon, lungo Retinoblastomas, osteosarcoma o p53o Cell cycle arrest and apoptosis in response to DNAo Most human cancerso Li-Fraumeni syndrome; multiple carcinomas and sarcomas o WT - lo Nuclear transcriptiono Wilms tumoro Wilms tumor o pi6 (INK 4a)o Regulation of cel l cycle by inhibition of cyclin dependent kinaseso Pancreatic, breast, and esophageal cancerso Malignant melanoma o BRCA - l and BRCA2o DNA repairo Unknowno Carcinomas of female breast and ovary ; carcinomas of male breast o KLF 6o Transcription factoro Prostateo UnknownC-myc, fos & RAS are oncogenes (not tumor suppressor genes).