Final answer:
The first virus using rolling-circle replication and the second virus using theta replication will both take approximately 30 seconds to replicate their genomes.
Step-by-step explanation:
The first virus uses rolling-circle replication which is a process in which replication begins at a specific site on the genome and moves in one direction around the circular genome. Since the DNA genome of this virus is 12 Kb, and it synthesizes DNA at a rate of 400 nucleotides per second, we can calculate the time it takes to replicate the genome as follows:
12 Kb = 12,000 nucleotides
Time = (nucleotides)/(rate) = (12,000 nucleotides)/(400 nucleotides/second) = 30 seconds
Therefore, the first virus will take approximately 30 seconds to replicate its genome.
The second virus uses theta replication which is a process in which replication begins at a single origin and moves in a bidirectional manner. Since the DNA genome of this virus is also 12 Kb and it synthesizes DNA at the same rate of 400 nucleotides per second, we can again calculate the time it takes to replicate the genome as follows:
Time = (nucleotides)/(rate) = (12,000 nucleotides)/(400 nucleotides/second) = 30 seconds
Therefore, the second virus will also take approximately 30 seconds to replicate its genome.