Solution:
Semi-conservative replication of DNA means that during replication out of the two strands present in one molecule of DNA, one is the old parental strand and other is the newly synthesised strand. This process was first demonstrated in E. coli in which the rate of semi-conservative DNA replication in a living cell was first measured as the rate of phage \(T_{4}\)-DNA strand elongation in phage infected E. coli.
