What is meant by the term semiconservative replication? What are the functions of DNA Pol I and III, helicase, and primase? How does a leading strand differ from a lagging strand?

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Semiconservative replication refers to the fact that DNA is replicated using a previously formed strand or parent strand. DNA duplicates when the double-stranded molecule splits into single strands (parent strands) and new complementary strands (daughter strands) are synthesized for each single strand. In other words, two strands becomes four strands; two of the strands, one on each double-stranded molecule, are from the original DNA molecule, and the other two strands, one on each double-stranded molecule, are newly replicated.

DNA Pol III plays a major role in chromosomal DNA replication/synthesis, while DNA Pol I plays a lesser role. Helicase unwinds the double-stranded DNA molecule, thereby exposing single template strands so that DNA synthesis can begin. Primase creates an RNA primer on a single parent strand of DNA, thereby setting the stage for DNA synthesis by DNA polymerase.

DNA synthesis is continuous on the leading strand and discontinuous on the lagging strand. This means that the leading strand requires only one RNA primer, while the lagging strand requires multiple RNA primers.