Tumor Supressor Genes – overview (2014)

– Normal cell proliferation is controlled by a balance of Proto-oncogenes and Tumor suppressor genes. – Proto-oncogenes encode for proteins involved in the stimulation of cell proliferation or differentiation. – Tumor suppressor genes encode for proteins which inhibit cell proliferation or stimulate apoptosis. So, activation of the tumor suppressor genes keep our cells from proliferating when there is damage to our DNA – With cancer, the tumor suppressor genes are inactivated or lost. Point mutations, deletions and epigenetic changes frequently result in inactivation of tumor suppressor genes in cancer. – For the epigenetic changes, she specifically mentioned methylation of the promotor sequence for the tumor suppressor gene. This methylation would block transcription of that gene. My notes – It can be caused by deletion or point mutation – It can be an epigenetic change i.e. not a change in genetic sequence but rather a change in methylation of the promoter (no longer accessible to TFs). More test answers on https://studyhippo.com/app-2b-cancer-1/

Tumor supressor genes – RB (2015)

a) First discovered in cases of familial retinoblastoma. In these families, offspring inherited 1 defective copy. Being born one step behind leaves these individuals open to a second mutation that would lead to loss of heterozygosity. Keep in mind that, although RB was discovered in families with retinoblastoma and named after the cancer, mutations in the RB tumor suppressor are implicated in MANY cancers, such as osteosarcomas, soft tissue sarcomas, or melanomas. b) Function: Gatekeeper at the G1-S phase checkpoint. This checkpoint is extremely important to prevent the replication of damaged DNA. c) Loss of function: obviously loss of this checkpoint would lead to a green light at the G1- S phase checkpoint at all times. d) If RB is expressed in all cells and guards a very important checkpoint in replication, why do inherited mutations only lead to familial retinoblastomas? Apparently, the only theory is that apoptosis is turned off in retinal cells during development and this increases their dependence on genes like RB, which ensure they replicate with high fidelity. More test answers on https://studyhippo.com/app-2b-cancer-1/

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What is Tumor Supressor Gene?

A tumor suppressor gene (TSG) is a gene that helps to prevent the development and growth of tumors. It does this by regulating cell growth, keeping cells from dividing too quickly or forming irregularly shaped cells. TSGs are important for maintaining a healthy balance between cell division and death, as well as regulating metabolic processes like inflammation. They also help to protect against genetic mutations that can lead to cancer.The most well-known TSG is the p53 gene, which is responsible for producing the protein p53. This protein works by detecting damage in DNA and triggering cell cycle arrest or apoptosis (programmed cell death). This allows time for repairs to be made before the damaged cells divide uncontrollably, leading to tumor formation. In addition to p53, there are other TSGs such as BRCA1 and BRCA2 which help repair damaged DNA and prevent double-stranded breaks in chromosomes that can lead to further mutations. Other important TSGs include VHL, PTEN, RB1, APC and NF1. Most cancers are caused by a combination of genetic changes in multiple genes (oncogenes), including changes in one or more of these tumor suppressor genes. A mutation in any one of these tumor suppressor genes can significantly decrease its ability to inhibit tumor formation; therefore it is important that they remain functional within our cells so they can continue their job properly. Genetic testing is available for many types of cancer-related mutations in these TSGs; however it is not always necessary unless a person has an increased risk due to certain family history factors. Knowing if you have inherited one of these weakened versions of a TSG may provide insight into your risk for developing certain types of cancer; however it does not guarantee that you will develop cancer nor does it guarantee protection from developing cancer either way.