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level: 20.5 Gene expression and cancer

Questions and Answers List

level questions: 20.5 Gene expression and cancer

QuestionAnswer
What is cancer ?- Uncontrolled Mitosis therefore cell division
Cell Division controlled by two genes- Proto-oncogenes (stimulate cell division) ACCELERATOR - Tumour Suppressor Genes (suppress cell division) BRAKE
Benign Tumour- Localised slow growing tumour that does not metastasise
Malignant tumour- A fast growing tumour that often metastasises
Metastasis- Where primary cancer cells break off and produce secondary cancers (often in the lymph notes)
Benign Tumours- Slow growing - Cells adhere to each other - Do not metastasise - Treated by surgery - Cells do show diferentiation
Malignant Tumours- ​Fast growing - Cells don't adhere to each other - Does metastasise - Treated by radiotherapy, chemo, surgery - Cells do not show diferentiation
Proncogenes- Genes that stimulate cell division e.g. they may encode growth factors or cell cycle regulators/ cause cancer - Many cancers are found to have cells with abnormal DNA methylation (epigenetic changes) - Detecting these changes can help diagnose, while reversing these changes may help cure these diseases
If there is a mutation in genes controlling mitosis cancers can develop:- Proto-Oncogenes become Oncogenes : these may lead to the constant production of growth factors - Or may lead to the receptor being activated so cell division is switched on permanently
Hypermethylated- Not enough methyl groups added - Turn on genes
Hypomethylated- Too many methyl groups added - Turn off genes
Proto-oncogenes can be hypomethylated- Oncogenes can be hypomethylated in the promoter regions, turned on, more proteins that control mitosis, more uncontrolled cell divison
Tumor suppressor genes- Tumour suppressor genes are genes that prevent tumour formation by repairing DNA damage, regulating cell division and promoting apoptosis
Tumour suppressor genes can be hypermethylated- Can be hyper. in promoter region to prevent transcription, turn off tsg, less proteins that control mitosis, more uncontrolled cell divisions with a higher mutation rate = cancerous tumours
So....- If we could produce a drug that would inhibit the enzyme that leads to methylation we could reduce the risk of some cancers - Identifying high or low methylation levels would help to identify patients at risk
Oestrogen and breast cancer- Binds to a transcription factor, which activates genes to promote cell division - Increased oestrogen concentrations in the adipose tissue in the breast of post-menopausal women has been linked to breast cancer development
How protooncogenes are used to initiate cell division- Proto-oncogene transcribed + translated to produce a protein (growth factor) - Growth factor binds to complementary shaped receptor on the cell membrane - This acts as a switch which activate transcription factors - The transcription factor binds to DNA + leads to the production of proteins that initiate mitosis - Therefore leading to cell division
BRCA 1- A tumour suppressor gene - Mutation is recessive