AP BIOLOGY

Detailed explanation-1: -The p53 gene has been shown to be involved in the control of the cell cycle, transcriptional regulation, DNA replication, and induction of apoptosis. The p53 gene can suppress cell transformation and malignant cell growth.

Detailed explanation-2: -In contrast to the cellular proliferation-stimulating function of proto-oncogenes and oncogenes that drive the cell cycle forward, tumor suppressor genes code for proteins that normally operate to restrict cellular growth and division or even promote programmed cell death (apoptosis).

Detailed explanation-3: -For example, TP53 is an important tumor suppressor gene. It codes for the p53 protein, which helps keep cell division under control. Inherited changes in the TP53 gene can lead to Li-Fraumeni syndrome.

Detailed explanation-4: -Tumor suppressor genes often function to restrain inappropriate cell growth and division, as well as to stimulate cell death to keep our cells in proper balance. In addition, some of these genes are involved in DNA repair processes, which help prevent the accumulation of mutations in cancer-related genes.

Detailed explanation-5: -Examples include BUB1, BUBR1, TGF-RII, Axin, DPC4, p300, and PPAR. The most frequent mechanism of inactivation of the second allele of a tumor suppressor gene is allelic deletion, and therefore loss of specific chromosomal regions occurs frequently in human neoplasia.