Molecular biology of cancer Flashcards
(26 cards)
Name the three competing models of cancer origins.
- Differentiation model
- Viral model
- Mutagenesis model
What is the Differentiation model ?
It is a model of cancer origins:
- Cancer is a misregulated developmental process
- Phenotypic changes are based on an epigenetic process
What is the Viral model ?
It is a model of cancer origins:
- Cancer is caused by infections with tumor viruses
- Several tumor-causing viruses were identified in animals and some in humans
What is the Mutagenesis model ?
It is a model of cancer origins:
- Cancer arises from DNA mutations in somatic cells
- Radiation and chemicals are linked to tumor formation
Name two genetic abnormalities which are common in cancer cells.
- Point mutations
- Chromosomal abnormalities
Name the two types of mutations in tumors depending on their functional relevance.
- Driver mutations: Causally linked to tumor behaviour
- Passenger mutations: Incedental or redundant
Not all changes in cancer cells are genetic. Name another reason for cancer development.
Epigenetic changes like methylation or histone modification
Name three types of single-gene alteration.
- Point mutation
- Insertion
- Deletion
How are fusion genes usually created ?
By chromosomal rearrangements
In point mutations exist two types of base exchanges. Name both and explain them shortly.
- Transitions: A purine is replaced by a purine or a pyrimidine is replaced by a pyrimidine
- Transversions: A purine is replaced by a pyrimidine or the other way around
What are silent mutations, missense mutations and nonsense mutations ?
- Silent: Codon change without amino acid change
- Missense: Amino acid change with a neutral, activating or inactivating effect
- Nonsense: Leads to a premature stop codon
What can be the consequences of mutations in the splice site ?
- Exon skipping
- Exon elongation
- Reading frame alteration
How can a chromosomal translocation effect the activation of genes ?
- By disrupting coding regions
- By altering regulatory regions
What are chromosomal inversions ?
- Intrachromosomal rearrangements
- Have the same functional effects as translocations
Name three consequences of chromosomal inversions.
- Gene disruptions
- Misregulation
- Formation of fusion genes
What is a mitotic nondisjunction ?
- Incorrect chromosome separation during anaphase of mitosis
- Leading to daughter cells with an abnormal number of chromosomes
What is a chromothripsis ?
A destructive and random reassembly of a single chromosome
What is a chromoplexy ?
A series of independent translocations involving multiple chromosomes
What is the main difference between chromothripsis and chromoplexy ?
- Chromothripsis: Intrachromosomal rearrangements
- Chromoplexy: Interchromosomal rearrangements
What does the abbreviation LOH mean?
- Loss of heterozygosity
- Only one allele remains
Name three mechanisms which can lead to a loss of heterozygosity (LOH).
- Whole chromosome loss
- Partial arm deletion
- Mitotic recombination
Name one example how a loss of heterozygosity (LOH) can lead to cancer development.
Silencing of tumor suppressor genes
What are the two major classes of cancer-related genes ?
- Oncogenes
- Tumor suppressor genes
What are oncogenes ?
Genes which promote cancer through increased or misdirected activity
