Summary
The leading strand is made continuously, while the lagging strand is made in short Okazaki fragments.
In depth
Because polymerase works only 5' to 3', one strand is made continuously toward the fork (leading) and the other discontinuously away from it (lagging). The lagging strand needs repeated priming, which makes the process more complex.
The replication fork is asymmetric but the polymerases are coordinated in a replisome.
The two strands are copied by a coordinated replisome with the lagging strand looping out so both polymerases move together. A new Okazaki fragment is started roughly every second in bacteria. This design costs primers and ligation, but it arises from the antiparallel structure of DNA and the fixed 5 prime to 3 prime direction of polymerases.
At termination, replication forks meet; in bacteria Tus-Ter sites trap forks to end replication opposite the origin. Linear eukaryotic chromosomes have a problem at the very end of the lagging strand that telomerase solves.
Example: in a drawing, the leading strand arrow points the same way as the fork, while lagging arrows point back away from it.
Frequently asked questions
What is Leading and Lagging Strands?
The leading strand is made continuously, while the lagging strand is made in short Okazaki fragments.
Which area of biology covers Leading and Lagging Strands, and how advanced is it?
Leading and Lagging Strands is one of the 52 topics in Molecular Biology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Primase and RNA Primer, Okazaki Fragments, DNA Polymerase.
Can you give an example of Leading and Lagging Strands?
The lagging strand has many more primers than the leading strand.
What should I learn before Leading and Lagging Strands?
Work through the Beginner topics in Molecular Biology first, such as Central Dogma, DNA Replication, Base Pairing, then return to Leading and Lagging Strands. Intermediate topics assume the Beginner vocabulary.
What topics are related to Leading and Lagging Strands?
The closest topics to Leading and Lagging Strands are Primase and RNA Primer, Okazaki Fragments, DNA Polymerase, DNA Replication. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Leading and Lagging Strands?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Leading and Lagging Strands. To practise the whole of Molecular Biology, use the Molecular Biology quiz.
How is Leading and Lagging Strands different from Primase and RNA Primer?
Leading and Lagging Strands: The leading strand is made continuously, while the lagging strand is made in short Okazaki fragments. Primase and RNA Primer: Primase lays down a short RNA primer that gives DNA polymerase a starting 3 prime end. Read both side by side and note what each one explains.
How should I study Leading and Lagging Strands step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Primase and RNA Primer and explain the difference aloud. Finally, take the Molecular Biology quiz and come back to this page for any question you miss.