Why is DNA replication referred to as semiconservative?

DNA replication is considered semiconservative because, during the process, each resulting double helix comprises one original (parental) strand and one newly synthesized strand. This means that when the two strands of the original DNA molecule separate, each serves as a template for the formation of a new complementary strand. As a result, the two resulting double helices each contain one strand from the original DNA and one newly formed strand. This mechanism ensures genetic continuity and accuracy, as the original strand guides the synthesis of the new complementary strand, maintaining the integrity of the genetic information passed on to daughter cells.

The other options do not accurately represent the semiconservative nature of DNA replication. For example, the notion of just one strand of DNA does not capture the full breadth of the process, and the idea that each helix contains two new strands would imply a different replication model altogether, negating the preservation of the original strand. Additionally, while replication does involve multiple stages, this is not what semiconservative refers to; it specifically highlights the composition of the new DNA molecules formed.