DNA replication is the biological process by which genetic information is duplicated to produce two identical copies of an organism’s genome. DNA replication occurs in all living organisms acting as the basis for biological inheritance. The cell possesses the distinctive property of division which makes replication of DNA essential.
DNA is made up of a double helix of two complementary strands. DNA replication begins at a site on the chromosome referred as the origin of replication. This site is recognized by an enzyme that opens up the two strands and allows helicase to further unwind the double helix, a process that is necessary for replication to continue.
As the helicase enzyme continues to open up the helix, it separates into two strands. The place where the two strands begin unwinding is referred to as the replication fork. These strands can be used to make new complementary strands referred to leading and lagging strand.
One of the most important enzymes in the process of replication is DNA polymerase. This enzyme is the one that carries the individual nucleotides to the side of replication. DNA polymerase builds the daughter strand by matching new nucleotides to their complementary bases on the parent strand.
When the DNA polymerase runs down a single strand of DNA it moves from the 3’ end to the 5’ end and it creates the second strand in the 5’ to 3’ direction. When polymerase moves towards the replication fork, the strand it’s on is referred to as the leading strand. When polymerase moves away from the replication fork (towards the origin), it’s on the lagging strand.
What Is A Leading Strand?
Leading strand is the parent strand of DNA which runs in the 3’ to 5’ direction towards the fork and it is able to be replicated continuously by DNA polymerase.
What You Need To know About Leading Strand
- Leading strand is a replicated strand of DNA which grows continuously without any gap.
- Leading strand does not require DNA ligase.
- Formation of leading strand begins immediately at the beginning of replication.
- The direction of growth of the leading strand is 5’->3’
- Leading strand requires a single RNA primer for the synthesis.
- Formation of the leading strand is quite.
- Leading strand template opens in 3’->5’ direction
What Is A Lagging Strand?
Lagging strand is the parent strand which runs in the 5’ to 3’ direction towards the fork and it’s replicated discontinuously.
What You Need To know About Lagging Strand
- Lagging strand is a replicated strand of DNA which is formed in short segment called Okazaki fragments. Its growth is discontinuous.
- Lagging strand requires DNA ligase to ligate Okazaki fragments together.
- Formation of lagging strand behind a bit later than that of the leading strand.
- The direction of growth of the lagging strand is 3’->5’, though in each Okazaki fragment it is 5’->3’
- Lagging strand requires a new RNA primer to start each Okazaki fragments.
- Formation of the lagging strand is quite slower.
- Lagging strand’s template opens in 5’->3’
Also Read: Difference Between Template And Coding Strand
Difference Between The Leading And The Lagging Strand In Tabular Form
| BASIS OF COMPARISON | LEADING STRAND | LAGGING STRAND |
| Description | Leading strand is a replicated strand of DNA which grows continuously without any gap. | Lagging strand is a replicated strand of DNA which is formed in short segment called Okazaki fragments. Its growth is discontinuous. |
| DNA Ligase | Leading strand does not require DNA ligase. | Lagging strand requires DNA ligase to ligate Okazaki fragments together. |
| Formation | Formation of leading strand begins immediately at the beginning of replication. | Formation of lagging strand behind a bit later than that of the leading strand. |
| Direction Of Growth | The direction of growth of the leading strand is 5’->3’ | The direction of growth of the lagging strand is 3’->5’ through in each Okazaki fragment it is 5’->3’ |
| RNA Primer | Leading strand requires a single RNA primer for the synthesis. | Lagging strand requires a new RNA primer to start each Okazaki fragments. |
| Speed Of Formation | Formation of the leading strand is quite. | Formation of the lagging strand is quite slower. |
| Opening | Leading strand template opens in 3’->5’ direction | Lagging strand’s template opens in 5’->3’ |