Problem
For senior research, you end up studying the life cycle of an animal virus whose genome consists of a single circular, double-stranded DNA molecule. The project is to define the number and location of the origin(s) of replication and to determine whether replication proceeds in one [unidirectional] or both [bidirectional] directions away from an origin. To accomplish this, you isolate many identical strands of DNA that have already been partially replicated. You cleave each piece of DNA exactly once with a restriction enzyme. You then observe the cut pieces of DNA using an electron microscope. Below is a schematic representation of what you observe. Remember each line represents a different piece of DNA, and not a fragment of a larger piece.
Using this data, answer the following questions:
i. How many origins of replication does the viral genome has, and why?
ii. Does the data support unidirectional or bidirectional replication of the viral genome? How have you come to this conclusion?