Final answer:
The synthesis on the leading strand during DNA replication is continuous, as the DNA polymerase enzyme synthesizes DNA in the 5' to 3' direction along with the movement of the replication fork. Option A is the correct answer.
Step-by-step explanation:
The type of synthesis that occurs on the leading strand during DNA replication is continuous. Unlike the lagging strand which synthesizes DNA in short, discontinuous stretches known as Okazaki fragments, the leading strand synthesizes DNA continuously in the 5' to 3' direction.
This is because the enzyme DNA polymerase can only add new nucleotides to the 3' end of the growing strand. As the replication fork opens up, the leading strand can be synthesized smoothly in the direction of the fork movement because its template is oriented in the correct direction for the polymerase to work continuously.
The enzyme primase synthesizes a short RNA primer which provides a starting point for DNA polymerase to begin synthesis. On the leading strand, only one RNA primer is needed at the origin of replication, while the lagging strand requires multiple primers.
Meselson and Stahl's experiments proved that DNA replication is semi-conservative, meaning that each new DNA molecule consists of one original and one newly synthesized strand. DNA replication is also bidirectional, starting from a single origin and proceeding in two opposite directions, and discontinuous on the lagging strand due to the direction of polymerase activity.
Therefore, the correct option answer is a) Continuous.