Nucleotides can be radiolabeled before they are incorporated into newly forming DNA and, therefore, can be assayed to track their incorporation. In a set of experiments, a student—faculty research team used labeled T nucleotides and introduced these into the culture of dividing human cells at specific times. Use the following information to answer the question below.
The research team used their experiments to study the incorporation of labeled nucleotides into a culture of lymphocytes and found that the lymphocytes incorporated the labeled nucleotide at a significantly higher level after a pathogen was introduced into the culture. They concluded that __________.
a. their tissue culture methods needed to be relearned
b. infection causes lymphocyte cultures to skip some parts of the cell cycle
c. infection causes cell cultures in general to reproduce more rapidly
d. the presence of the pathogen made the experiments too contaminated to trust the results
e. infection causes lymphocytes to divide more rapidly