Exam (elaborations)
Cancer (8) Questions with Accurate Answers
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Exam of 9 pages for the course cancer at cancer (Cancer (8))
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Cancer (8)Mutations in genes - answer• Mutations that occur in individual cells after fertilization
(e.g. in adulthood) are called acquired mutations
• If these mutations occur in the genes that control the rate of cell division (by mitosis), it
can cause uncontrolled cell division
• If a cell divides uncontrollably the result is a tumor- a mass of abnormal cells
>tumors that invade and destroy surrounding tissue are called cancers
• There are two types of gene that control cell division- tumor suppressor genes and
proto-oncogenes
>mutations in these genes can cause cancer
Tumors - answer Can develop for years without any obvious symptoms and can be
quite large by the time they're discovered
Malignant tumours - answer• Are cancers
• They usually grow rapidly and invade and destroy surrounding tissues
• Cells can break off the tumours and spread to other parts of the body in the
bloodstream or lymphatic system
Benign tumours - answer• Are not cancerous
• They usually grow slower than malignant tumours and are often covered in fibrous
tissue that stops cells invading other tissues
• Benign tumours are often harmless, but they can cause blockages and put pressure
on organs
• Some benign tumours can become malignant
How tumour cells can differ to normal cells - answer• They have an irregular shape
• The nucleus is larger and darker than in normal cells
>sometimes the cells have more than one nucleus
, • They don't produce all the proteins needed to function correctly
• They have different antigens on their surface
• They don't respond to growth regulating processes
• They divide (by mitosis) more frequently than normal cells
Abnormal methylation of cancer-related genes - answer• Methylation means adding a
methyl group onto something
• Methylation of DNA is an important of regulating gene expression
>it can control whether or not a gene is transcribed (copied into mRNA) and translated
(turned into a protein)
• When methylation is happening normally, it plays a key role in many processes in the
body
>it's only when it happens too much (hypermethylation) or too little (hypomethylation)
that it becomes a problem
• The growth of tumours can be caused by abnormal methylation of certain cancer-
related genes
Hypermethylation - answer• When tumour suppressor genes are hypermethylated, the
genes are not transcribed
>so the proteins they produce to slow cell division aren't made
>this means that cells are able to divide uncontrollably by mitosis and tumours can
develop
Hypomethylation - answer• Hypomethylation of proto-oncogenes causes them to act as
oncogenes
>increasing the production of the proteins that encourage cell division
>this stimulated cells to divide uncontrollably, which causes the formation of tumours
Increased oestrogen and breast cancer - answer• Increased exposure to oestrogen over
an extended period of time is thought to increase a woman's risk of developing breast
cancer
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