8.2.4 The ras Gene and the p53 Gene Flashcards
1
Q
ras gene
A
- a proto-oncogene that codes for a protein that is involved in a signal-transduction pathway that stimulates
the cell cycle. A mutation in the ras gene can lead to excessive cell division. - codes for a protein involved in a signal-transduction pathway that stimulates the cell cycle. In a typical signal-transduction pathway, a growth factor (from outside of the cell) will bind to a protein receptor that is embedded in the cell membrane. Once the growth factor binds to the receptor, the receptor will pass a signal onto the
ras protein, located inside of the cell. The ras protein then sends a message down a series of proteins that will eventually arrive at a transcription factor, which will stimulate gene expression of a protein that will, in turn, stimulate the cell cycle. If the ras gene is defective, the cell cycle could end up being stimulated all of the time, even without growth factor.
2
Q
p53 gene
A
- a tumor-suppressor gene that inhibits the cell cycle and triggers apoptosis (cell death) in cells that have
damaged DNA. - involved in 50 percent of human cancers. The p53 gene is a tumor-suppressor gene that codes for a transcription factor that is necessary for RNA polymerase to bind to DNA to make several proteins including p21 (a protein that stops the cell cycle), DNA repair proteins, and “suicide” proteins that trigger apoptosis.
3
Q
The ras gene
A
- codes for a protein involved in the stimulation of the cell cycle
4
Q
True or false?
A defective p53 gene will not be able to activate the transcription of other genes.
A
- true
5
Q
The p21 gene
A
- halts the cell cycle
6
Q
Which statement regarding proto-oncogenes is correct?
A
- Proto-oncogenes are normally involved in the regulation of cell division
7
Q
Which statement regarding the p53 gene is not true?
A
- The p53 gene encodes a protein kinase involved in the last step of a phosphorylation cascade
8
Q
Which of the following genes codes for a G protein that relays a growth signal?
A
- ras
