What is difference between the leading and lagging strands in DNA replication?
Which?
Okazaki fragments are connected together with DNA polymerase.
The lagging strand has continuous DNA replication.
The leading strand produces short DNA fragments that get combined later.
The leading strand makes one, long piece of DNA.
The DNA polymerase on the lagging strand moves in the same direction as the replication fork.
The correct answer and explanation is :
The correct statement is:
The leading strand makes one, long piece of DNA.
Explanation:
DNA replication is a highly regulated and intricate process in which DNA is copied to produce two identical molecules of DNA, ensuring accurate genetic information is passed on during cell division. Replication occurs at the replication fork, where the DNA strands separate to form two single-stranded templates. These templates are used to synthesize new DNA strands, with one strand being copied continuously and the other in short fragments.
In DNA replication, there are two strands involved: the leading strand and the lagging strand. These two strands behave differently due to the directionality of the DNA and the nature of the enzyme DNA polymerase, which can only add nucleotides in the 5′ to 3′ direction.
- Leading Strand:
- The leading strand is synthesized continuously in the same direction as the replication fork is moving (5′ to 3′ direction).
- It is synthesized in one continuous piece because the direction of replication is aligned with the unwinding of the DNA.
- This allows the DNA polymerase to keep adding nucleotides in a smooth and uninterrupted manner.
- Lagging Strand:
- The lagging strand is synthesized discontinuously in the opposite direction (3′ to 5′) of the replication fork.
- Since DNA polymerase can only synthesize DNA in the 5′ to 3′ direction, the lagging strand is created in short fragments known as Okazaki fragments.
- Each fragment is synthesized in the 5′ to 3′ direction, but because the strand is oriented in the opposite direction to the replication fork, new fragments are made in segments, and these fragments must later be connected.
After the Okazaki fragments are synthesized, the enzyme DNA ligase connects them together, forming a continuous strand.
Key Points:
- The leading strand synthesizes DNA continuously, producing one long piece.
- The lagging strand is synthesized in short fragments (Okazaki fragments) due to the directionality issue.
- DNA ligase is responsible for joining these Okazaki fragments into a continuous strand.
Thus, the leading strand is synthesized in one long piece, while the lagging strand involves short fragment synthesis that is later connected.