What are the events that mark the beginning and the end of the second interphase period? What happens in the cell in this period?
The second interphase period is the S. It begins with the beginning of DNA replication and finishes with the end of that process. The main event in this period is the synthesis of new polynucleotide chains, each bound to each DNA chain that served as a template, i.e., the duplication of the original set of DNA molecules.