15.) Oncogenes and Cancer Genetics Flashcards
Define proto-oncogene.
These are genes that have the potential to be mutated into oncogenes.
Define oncogene.
This is a mutated or over-expressed gene that causes cancer.
What is a reverse-transcriptase?
This is an enzyme that can transcribe an mRNA into a DNA segment. Found in retroviruses, which can incorporate this synthesized DNA segment into its host cell.
What is a gain of function mutation?
This is a mutation that will cause a protein to gain a new function, or cause over expression of the gene. (confirm this)
What is a loss of function mutation?
This is a mutation that causes the inactivation of the gene/protein. (confirm this)
What types of proteins are possible candidates for conversion to an oncogene?
- ) Growth Factors
- ) Growth factor receptors
- ) Intracellular signal transducers (eg cyclins)
- ) Nuclear transcription factors
What is penetrance? Expressivity? Expand on the important difference between these two definitions.
Penetrance: passing of a mutated gene to an offspring.
incomplete penetrance– only some of your offspring inherit the gene.
Expressivity: severity of expression of the phenotype in diff individuals with the same disease-causing genotype.
important difference– offspring who inherits a mutated gene (penetrance) may have different expressivity. Ie penetrance = genotype; expressivity=phenotype.
What is the two-hit hypothesis?
Was used to explain the early onset at multiple sites in the body of an inherited form of cancer (retinoblastoma).
Inheriting one germline copy, not sufficient for cancer development.
Loss of the good gene, occurring through a somatic process, leads to cancer development.
Hypothesis: The chances for a germline mutation carrier to get a second somatic mutation was much greater than for a non-carrier to develop two hits in the same cell.
When severity of a disorder varies in people with the same genotype, then the gene has ______________.
variable expressivity
