Question

what do you meant by semi-conservative mode of replication of DNA?

Answer 1

The semi-conservative mode of DNA replication suggests that after the completion of replication, each new DNA double helix molecule retains (conserves) one of the two strands of the original DNA double helix.
During DNA replication, both the stands separate from each other and act as template for synthesis of new strands. So after DNA replication, two double stranded molecules of DNA are synthesised, each one with one parental strand (template) and the one newly synthesised strand.