1.) Most transduction systems for hormones and sensory stimuli that involve trimeric G proteins have in common all of the following except:

A) cyclic nucleotides.
B) nuclear receptors.
C) receptors that interact with a G protein.
D) receptors with multiple transmembrane segments.
E) self-inactivation.

2.) The G-protein involved in visual signal transduction is:

A) a leukotriene.
B) transducin.
C) arrestin.
D) rhodopsin.
E) a GTP receptor.

3.) Which of the following statements concerning cyclin-dependent protein kinases is not correct?

A) Each type of cell contains one specific form (isozyme).
B) Their activity fluctuates during the cell cycle.
C) Their activity is regulated by changes in gene expression, protein phosphorylation, and proteolysis.
D) Their activity is regulated by cyclins.
E) They can alter the activity of proteins involved in the progression of cells through the cell cycle.

4.) Which of the following statements concerning cyclins is not correct?

A) They are activated and degraded during the cell cycle.
B) They are regulatory subunits for enzymes that catalyze the phosphorylation of proteins.
C) They can become linked to ubiquitin.
D) They catalyze the phosphorylation of proteins.
E) They contain specific amino acid sequences that target them for proteolysis.

5.) Proto-oncogenes can be transformed to oncogenes by all of the following mechanisms except:

A) chemically induced mutagenesis.
B) chromosomal rearrangements.
C) during a viral infection cycle.
D) elimination of their start signals for translation.
E) radiation-induced mutation.