10. Which of the following experiments can test your hypothesis?
Choose between irrelevant, possible and recommended.

A. Analysis of substance X effect on CDK2 and CDK4 ability to phosphorylate pRb using  phosphopeptide mapping of pRb. Possible CDK2 and CDK4 phosphorylate pRb on different residues. Examining the phosphorylation of these residues will show the differential effect of substance X on CDK4 and CDK2 activities. However, this method is more complicated than others and requires equipment that may not be available in your lab.

B. Analysis of substance X effect on CDK2 and CDK4 immunocomplexes ability to phosphorylate histone H1 or pRb in-vitro. Recommended

C. Analysis of substance X effect on p21 and p27 levels in CDK2 containing complexes. Possible but wouldn't it be better first to show that CDK2 kinase activity is impaired following exposure to substance X?

D. Analysis of substance X effect on T161 phosphorylation levels in CDK1. Irrelevant CDK1 is not involved in cell cycle progression before mid S-phase.