LiroxtronIV (LiroxtronIV)-
Why mitotic cell cycle tightly regulated?
cell cycle tightly regulated as it is important for normal cell division, development > cell cycle controlled by 3 checkpoints; G1, G2 & M checkpoint determine if cell cycle can proceed > checkpoints ensure key processes such as DNA replication is accurate/ bring about DNA repair mechanisms if required > prevents dysregulation of checkpoints of cell division, prevents excessive cell cycle progression & uncontrolled cell division which leads to tumour formation & possibly cancer
-
How uncontrolled cell division arises from loss of fn mutation in TSG p53?
loss of fn mutation in BOTH copies of p53 gene results in non-functional p53 protein > disrupts ability of cell to arrest cell cycle/activate DNA repair/trigger apoptosis, leading to uncontrolled cell division
-
How uncontrolled cell division arises from gain of fn mutation in POG ras?
gain of fn mutation in 1 copy of ras gene results in excessive amounts/hyperactive/degradation-resistant Ras protein > leads to uncontrolled cell division; Ras protein increases cell division even in absence of growth factors
-
Outline the development of cancer as a result of a causative agent.
development of cancer is multi-step process, requires accumulation of mutations in single cell, angiogenesis & metastasis >
causative agent causes gene mutations(bp sub/addition/deletion) in genes controlling checkpoint of cell cycle >
GOFM in 1 copy of POG results in excessive amounts of protein products leads to uncontrolled cell division OR
LOFM in both copies of TSG results in non-functional protein products which disrupts ability of cell to arrest cell cycle leads to uncontrolled cell division >
mutations in same somatic cell results in rate of cell division>rate of cell death, leading to uncontrolled cell division & tumour formation >
angiogenesis, growth of new blood vessels occurs within tumour to transport O2, nutrients to support growth of tumour >
cells of tumour invade surrounding tissue & metastasise to other sites, tumour considered malignant; cancer has developed
-
Define proto-oncogene
gene which codes for proteins involved in regulation of normal cell growth, cell division >
when mutated, oncogene >
oncogene expression leads to increase in amount of POG protein/ intrinsic activity of protein(hyperactive/degradation resistant)
-
Define tumour supressor gene
gene which codes for proteins that inhibit cell division, help to prevent uncontrolled cell growth, cell division >
protein products activate cell cycle arrest/DNA repair/apoptosis >
when mutated, decrease in activity of TS protein
-
What are the causative causes of cancer?
1. genetic predisposition
2. chemical carcinogens SUCH AS tobacco, ethidium bromide, asbestos
3. ionising radiation SUCH AS nuclear radiation, X-rays, gamma rays, UV radiation
4. age, loss of immunity
