Cancer Genetics Flashcards
Why do cancer cells behave in an abnormal manner?
Changes in the DNA sequences of key genes which are known as cancer gene
All cancers are genetic diseases
Give an example of how genetic defects cause cancer?
Colon cancer begins with a defect in a tumour suppressor gene that allows excessive hyperproliferation
Proliferating cells acquire additional mutations involving DNA repair genes, other tumour suppressor genes and growth related genes
What are some different types of cancer?
Carcinomas
Sarcomas
Lymphomas
Leukemias
What can cause cancer?
Environment
Viruses (exogenous factor)
Hereditary
What are the six hallmarks of cancer?
Self-sufficiency in growth signals Insensitivity to anti-growth signals Evading apoptosis Limitless replicative potential Sustained angiogenesis Tissue invasion and metastasis
What are the updated hallmarks of cancer?
Genome instability and mutation
Deregulation cellular energetics
Avoiding immune destruction
Tumor proliferating inflammation
What is a germline mutation?
Gene change in body’s reproductive cells
Hereditary
What is a somatic mutation?
Occur during mitosis anywhere in the body
Non-heritable
What can identify cancer germline mutations?
Positional cloning linkage studies
What are the different types of mutation?
Deletions Duplications Inversions Translocations Single base substitutions Chromosome instability Aneuploidy
What can identify cancer somatic mutations?
In vitro studies
How can excessive sun exposure cause cancer?
DNA damage from UV radiation leads to the formation of covalent bonds between two adjacent pyrimidines
C>T
What is a passenger mutation?
Mutation that can be tolerated by somatic cells
What is driver mutation?
Few mutations can confer a selective advantage and are recurrently found in homozygous state
Describe the trend show between cancer rates and frequency of division
The life time risk of developing cancer in a particular tissue is correlated with how often stem cells is that tissue divide
Why is cancer not simply due to ‘bad luck’?
100% of cancers are genetic
Terrible message, suggest lifestyle factors are not to blame
What is an oncogene?
A mutation in these genes cause the cell to become oncogenic
Results in cancer
One mutation is sufficient i.e. dominant
How are oncogenes activated?
Chromosome rearrangements, gene duplication or mutation
What is RAS?
Small protein present on plasma membrane
Activates many kinases affecting cellular processes
What happens to RAS that causes cancer?
A valine substitution
Cells continually proliferate
True or false, inherited mutations in oncogenes are very common
False
Give examples of some hereditary cancers?
Hereditary gastrointestinal stromal tumors
Hereditary papillary renal cancer
Malignant melanoma
What do tumour suppressor genes do?
Act to break excessive proliferation
Cause apoptosis if there is too many DNA defects
Recessive
Loss of function
Name a form of cancer caused by mutation in a tumour suppressor gene?
Retinoblastoma
