<prompt> True about p53 -a Tumor suppressor geneb Protooncogenec Proapoptoticd Encodes 53KDe Arrest cell cycle in G1bcebdeabcdacde  <response>: p 53 is a tumor suppressor gene and it is aproapoptotic factor, i.e. it promotes apoptosis if repair of DNA damage is unsuccessful at G1 arrest. The name p53 is in reference to its apparent molecular mass; it runs as a 53 kilodalton Kda protein on SDS-page. But based on calculations from its amino acid residues, p53s mass is actually only 43.7 K Da. P53 Guardian of the Genome Molecular Policeman The p53 gene is located on the short arm p of chromosome 1717pl3.1 It is the most common target for genetic alteration in human tumors Q A little over 50 of human tumors contain mutations in this gene The p53 gene derives its name from its apparent molecular mass It is a 53 k D proteinQ The major functional activities of the p53 protein are cell -cycle arrest initiation of apoptosis in response to DNA damage Normal Wild Type it function as a tumor suppressor gene function as a critical gatekeeper against the deveiopment of cancel Q The p53 gene is located in the nucleus functions as a nuclear transcription factor Two major functions are: In blocking mitotic activity: p53 inhibit cyclins cyclin dependent kinaseCDK prevents the cell to enter G1 phase transiently .This allow the normal cell to repair the DNA damage In promoting apoptosis : p53 gene directs cells that have damaged DNA to apoptosis by activating apoptosis inducing BAX genes thus brings the defective cells to an end. This process operates in the cell cycle at G1 G2 phase before the cell enters theS or M phase Q Mutant p53 gene The wild type of p53 gene may undergo mutations that inactivates or alter the normal function of p53 Presence of mutant p53 gene in tumor celts predicts apoor response to radiotherapy chemotherapy poor prognostic factor Q Inheritance of one mutant p53 allele predisposes individua Is to develop malignant tumors because only one additional hit is needed to inactivate the second normal allele- second hit phenomenon Q Most p53 mutation are acquired in somatic cells that inactivate or alter the normal function of p53 gene Tumors expressing mutantp53 genes are more resistant to radiation therapy chemotherapy than tumors with wild type p53 