Context: Conditional mutations express their mutant phenotype only under certain conditions (restrictive conditions) and the normal phenotype under normal conditions (permissive conditions). One type of conditional mutation is temperature-sensitive, which expresses the mutant phenotype only at certain temperatures.
Different cells containing temperature-sensitive mutations in the genes encoding different components of the DNA replication machinery have been isolated. In each of the following cells, the protein produced by the mutated gene is nonfunctional under the restrictive conditions. These cells are grown under permissive conditions and then abruptly switched to the restrictive condition. After one round of cell division under restrictive conditions, the DNA from each cell is isolated and analyzed. Assume that every other protein functions normally and that DNA replication will proceed as far as possible under restrictive conditions.
Question:
What would you predict to see in the DNA isolated from each cell if DNA ligase was mutated?
Please justify your predictions based on the information provided about the nature of the conditional mutations and the function of DNA ligase in DNA replication.
