Nucleotides can be radiolabelled before they are incorporated into newly synthesised DNA and, therefore, can be assayed to track their incorporation. In a set of experiments, a student-faculty research team used labelled T nucleotides and introduced these into a culture of dividing human cells at specific times. Which of the following questions might be answered by using the method described?
A) How many cells are produced by the culture per hour?
B) What is the length of the S phase of the cell cycle?
C) How many picograms of DNA are made per cell cycle?
D) When do spindle fibres attach to chromosomes?

Question

Quizplus · Accepted Answer

By tracking the incorporation of radiolabelled T nucleotides into newly synthesised DNA, the length of the S phase (during which DNA synthesis occurs) of the cell cycle can be determined.

Answer: C 
 By measuring the amount of radiolabelled T nucleotides incorporated into newly synthesised DNA, the total amount of DNA synthesised per cell cycle (and, therefore, per cell) can be determined.

Answers A and D cannot be answered by the method described as they do not directly relate to the incorporation of radiolabelled nucleotides into newly synthesised DNA.

Nucleotides Can Be Radiolabelled Before They Are Incorporated into Newly