Figure 13.1
- Figure 13.2
In an experiment, DNA is allowed to replicate in an environment with all necessary enzymes, dATP, dCTP, dGTP, and radioactively labeled dTTP (3H thymidine). After several minutes, the DNA is switched to nonradioactive medium and is then viewed by electron microscopy and autoradiography. Figure 13.2 represents the results. It shows a replication bubble, and the dots represent radioactive material. Which of the following is the most likely interpretation of the results?
A) There are two replication forks going in opposite directions.
B) Thymidine is being added only where the DNA strands are farthest apart.
C) Thymidine is being added only at the very beginning of replication.
D) Replication proceeds in one direction only.

Question

Figure 13.1
- Figure 13.2
In an experiment, DNA is allowed to replicate in an environment with all necessary enzymes, dATP, dCTP, dGTP, and radioactively labeled dTTP (3H thymidine). After several minutes, the DNA is switched to nonradioactive medium and is then viewed by electron microscopy and autoradiography. Figure 13.2 represents the results. It shows a replication bubble, and the dots represent radioactive material. Which of the following is the most likely interpretation of the results?
A) There are two replication forks going in opposite directions. 
B) Thymidine is being added only where the DNA strands are farthest apart. 
C) Thymidine is being added only at the very beginning of replication. 
D) Replication proceeds in one direction only.

Quizplus · Accepted Answer

The replication bubble and the presence of radioactive material suggest that there are two replication forks moving in opposite directions. Thymidine is likely being added to both strands as they are replicated.

Figure 13.1 - Figure 13.2