DNA replication follows a semiconservative mechanism . When E. coli incorporates radioactive thymidine during its initial replication, the newly synthesised strands become radioactive. If these bacteria are then transferred to a normal medium for further replication, the radioactive strands act as templates for the synthesis of new, non-radioactive complementary strands . Following the Watson-Crick model, each resulting daughter DNA molecule will possess one parental strand and one newly synthesised strand . Consequently, in the hybrid molecules formed, one strand is radioactive while the other is normal. This principle was experimentally proven by Taylor and colleagues using radioactive thymidine . Mastering these molecular biology experiments is a critical strategy, as NCERT textbooks serve as the primary source for approximately 95% of NEET Biology questions .