Difference between Lagging and Leading Strand

DNA replication is the first step of the central dogma where the DNA strands are replicated to make copies. During the process of replication the double stranded DNA is separated from each other by the help of enzymes like topoisomerases and helicases. The separated DNA strands form a replication fork, where both the DNA strands get replicated forming a lagging and leading strand.

The major difference between a lagging and leading strand is that the lagging strand replicates discontinuously forming short fragments, whereas the leading strand replicates continuously. Find out more such differences between a lagging and leading strand, in the table below.

Lagging Strand

Leading Strand


The strand that opens in the 3’ to 5’ direction towards the replication fork is referred to as the lagging strand.

The strand that runs in the 5’ to 3’ direction in the replication fork is referred to as the leading strand.


The strand is replicated discontinuously.

The strand is replicated continuously.


Short stretches called okazaki fragments are formed during replication.

No short fragments are formed.

Primer Requirements

Each fragment requires its own set of primers.

It requires only one primer.

Ligase Requirement

It requires DNA ligase enzymes for the joining of short okazaki fragments.

It does not require DNA ligase.

Direction of Growth

It grows away from the replication fork.

It grows in the direction of the replication fork.


The synthesis of new strands is slow.

The synthesis of new strands is fast.

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Frequently Asked Questions


Why is the leading strand able to replicate continuously but the lagging strand isn’t?

Replication is continuous in a leading strand because the template strand runs in the 3’ to 5’ direction, therefore it is replicated continuously as DNA polymerase catalyses polymerisation in only one direction, that is 5’ to 3’. The lagging strand has the DNA polymerase running away from the fork, so it has to come off and reattach every time to the newly exposed strand.


Does the lagging strand need a primer?

Yes, the lagging strand needs a new primer everytime a new fragment is synthesised.


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  1. The solution was very helpful for me thank you very much