You have determined that HeLa cell RNA labeled during 1- to 5-min incorporation period has a DNA-like base composition, whereas that labeled during a 30- to 60-min incorporation period has a rRNA-like base composition. In a pulse-chase experiment, you incubate HeLa cells with a radioactive RNA precursor for 5 min and then add actinomycin D. After 0-, 15-, and 60-min chases, you assay whole-cell extracts for RNA species by sedimentation analysis and for total incorporated radioactivity by liquid scintillation spectroscopy.a.) What results do you expect to observe?b.) Explain the difference in base composition of the RNA labeled during a 5-min period and a 60-min period.
Moved to appropriate forum. Bob.