Molecular Biology of the Gene 7th Edition by Richard Losick, James Watson, Michael Levine, Tamara Baker, Alexander Gann

Exercise 6

Tissières and Hopkins studied the relationship between DNA and protein synthesis. In one experiment, they measured the incorporation of amino acids into proteins in the presence of the enzyme deoxyribonuclease (DNase). They incubated a crude E. coli extract with varying concentrations of DNase for 10 min before adding the necessary components for the protein synthesis reaction including 14 C-labeled alanine. The amount of radioactivity incorporated is represented as cpm (counts per minute) in the data summarized below.

A. What effect does the addition of DNase have on protein synthesis?
B. From what you know about the central dogma, explain why the addition of DNase causes the effect on amino acid incorporation observed.
Data adapted from Tissières and Hopkins (1961. Proc. Natl. Acad. Sci. 47: 2015-2023).