If Cells Are Provided with Nucleotides Labeled with a Radioactive

Multiple Choice

If cells are provided with nucleotides labeled with a radioactive isotope of hydrogen (³H) ,newly synthesized DNA will be radioactively labeled.In a set of experiments,a student-faculty research team introduced labeled T nucleotides into cultures of dividing human lymphocytes at specific times.A pathogen was introduced into one culture prior to the start of the experiment,and another culture was left untreated as a control.Following a 24-hour incubation with the radiolabeled nucleotides,cells were lysed,and the DNA was isolated and tested for presence of radioactivity.The research team found that lymphocytes exposed to a pathogen incorporated three times the amount of labeled nucleotide as the control.Which of the following hypotheses might explain these observations?

A) The pathogen thrived in culture and incorporated the excess nucleotide.
B) Infection causes lymphocyte cultures to skip some parts of the cell cycle.
C) Infection causes lymphocytes to reproduce more rapidly.
D) Infection causes cell cultures in general to reproduce more rapidly.