Flashcards in Week 120 - Genes and Cancer Deck (17):
Why do cancers occur?
Majority due to mutations in the DNA that control cell growth and proliferation
A small proportion of cancers are thought to be inherited (~5%)
What is cancer?
A group of disorders that cause cells to:
- escape normal controls on cell division
- migrate from original site to other parts of body
What are the causes of cancer?
Environmental causes (e.g. smoking)
What are the characteristics of cancer cells?
Cancer cells form tumours with growth, whereas normal cells form flat sheets of cells
What is transformation when talking about cancer?
A multi-step process where a cell's growth goes from being regulated to un-regulated leading to uncontrolled proliferation
What are the two types of mutations that occur?
Acquired mutations (somatic mutations)
- do not occur in germ line cells
- germ line mutations
- present in every cell in the body
What percentage of cancer deaths are associated with smoking?
50 - 60%
Which cancers is smoking strongly linked to?
List four things which are strongly related to cancer
Viruses (DNA viruses strongly linked)
Radiation (UVB from sun can damage DNA)
Oncogenes (mutated from proto-oncogenes)
Give a few examples of viruses that are linked to cancer
Cervical cancer - HPV 16 & 18
Liver cancer - Hep B and Hep C
Kaposi's sarcoma and lymphoma - HIV
Briefly list the phases of the cell cycle
Non-dividing cells go from G1 and remain in G0
List the three main actions during interphase
G1 = cell undergoes normal metabolism and prepares for S phase
- check 1: check correct size of cell and for DNA damage
S = DNA replication occurs
- check 2: checks whether DNA has replicated correctly
G2 = cell prepares for mitosis
- check 3: checks whether mitotic spindle has formed properly
What is the function of P53?
A tumour suppressor gene that targets cells with severe DNA damage => apoptosis
Note: mutations to P53 => loss of tumour suppression => unregulated cell growth
What is the function of telomerase, and how is it affected in cancer?
Increases the length of telomeres to inhibit cell senescence
Telomerase increases in cancer
The proportion of individuals with a mutated gene that gain the disease
What is the effect of methylation of a gene?
Turns the expression of a gene off