Lectures 1/2 Flashcards
What is cancer?
Cancer is a condition where abnormal cells grow and reproduce uncontrollably.
What evidence is there for cancer being genetic?
-most carcinogens are also mutagens
-no mini epidemics so not contagious
-incidence increase with age in correlation with DNA damage
-chromosome instability a common feature
-defects in DNA repair increase probability of cancer
What are the two types of mutation?
Somatic and Germ line
What are germ-line mutations?
-mutations in every cell in the body
-passed directly from parent to child
-less common than somatic
-called inherited cancer
What are somatic mutations?
-known as acquired mutations
-occur due to damages to genes during a persons lifetime
-aren’t passed from parent to child
-most common cause of cancer
-called sporadic cancer
What are cancer genes?
Genes that before mutation have a normal function but once mutated can cause cancer
What are the two main groups of cancer genes?
Oncogenes and Tumor suppressor genes
What is the normal version of oncogenes?
Proto-oncogenes
Are oncogenes dominant or recessive?
Tend to be dominant acting
Can mutations in oncogenes be inherited?
Not usually
Do Timor suppressor genes act recessively or dominantly?
Recessive acting
Can tumor suppressor genes mutations be inherited?
Can be inherited in family cancer syndromes
What are the usual function of Timor suppressor genes?
Usually prevent cell growth/division
What happens when a tumor suppressor gene mutates?
You get a loss of function
Example of an inherited tumor suppressor gene cancer?
Retinoblastoma
What do Proto-oncogenes have as a usual function?
To promote cell growth and division
What happens when a proto-oncogene becomes an oncogene?
Gain of function mutation
What type of mutations occur in oncogenes?
Tend to have multiple mutations in a few codons affecting particular domains usually bias towards missense mutations
What type of mutations occur in tumor suppressor genes?
Usually missense mutations and mutations that cause premature termination
What are gatekeeper genes?
Act directly to restrain proliferation
What are caretaker genes?
Act directly and maintain integrity of genome. Disruption leads to genomic instability DNA repair genes are a subgroup.
What are landscaper genes?
Act indirectly to control the environment in which cells grow creating a microenvironment to aid cancer cells when mutated
What are DNA repair genes?
A subclass of tumor suppressor genes indirectly involved in growth, inhibition or differentiation.
What happens after inactivation of DNA repair genes?
-results in DNA damage going unrepaired
-leads to accumulation of mutations in the other cellular genes
-increasing the likelihood of damaging mutations in other genes
What is retinoblastoma?
Common eye tumor is a tumor of the retinal stem cell.
What are the signs of retinoblastoma?
Signs can be a white pupil
What is the two-hit hypothesis?
Also known as the Knudson hypothesis, says that it takes both alleles to be inactived through mutations or epigenetic silencing.
Why do inherited cancer occur earlier in life?
As they only need one mutation where as sporadic need two.
What is loss of heterozygosity (LOH)?
A mutation where you lose one normal copy of a gene or a group of genes.
