What is the main reason for there being both a leading strand and a lagging strand during DNA replication quizlet?

A) Breaks hydrogen bonds, unwinding DNA double helix.
B) Synthesizes RNA primers on leading and lagging strands.
C) Replaces RNA primers with DNA nucleotides.
D) Catalyzes phosphodiester bond formation, joining DNA fragments.
E) lagging strand
F) Leading Strand
G) Relaxes supercoiled DNA.
H) Coats single-stranded DNA, preventing duplex formation.
I) Synthesizes DNA 5' to 3' on leading and lagging strands.

uring replication, DNA synthesis occurs in the 5′ to 3′ direction along both template strands.
On one template strand, synthesis proceeds continuously toward the replication fork, generating the leading strand.
On the other template strand, DNA is synthesized away from the replication fork in segments called Okazaki fragments, generating the lagging strand.
Several proteins are involved in DNA replication, including the following:
Helicase breaks the hydrogen bonds between the parental DNA strands and unwinds the double helix.
Single-stranded binding proteins bind to the single strands of DNA, preventing them from reannealing and allowing synthesis to occur on both strands.
DNA polymerase III synthesizes the new strands, but it requires an existing 3′ hydroxyl (—OH) group to add nucleotides.
Primase creates short RNA primers, initiating DNA synthesis on both template strands.
DNA polymerase I removes the RNA primers and replaces them with DNA nucleotides.
On the lagging strand, DNA ligase joins Okazaki fragments by forming phosphodiester bonds between them, thus completing DNA replication.

a) -->
b) -->
c) <--
d) <--

DNA polymerase III can only add nucleotides to the 3' end of a new DNA strand. Because the two parental DNA strands of a double helix are antiparallel (go from 3' to 5' in opposite directions), the direction that DNA pol III moves on each strand emerging from a single replication fork must also be opposite.
For example, in the replication fork on the left, the new strand on top is being synthesized from 5' to 3', and therefore DNA pol III moves away from the replication fork. Similarly, the new strand on the bottom of that same replication fork is being synthesized from 5' to 3'. But because the bottom parental strand is running in the opposite direction of the top parental strand, DNA pol III moves toward the replication fork.
In summary, at a single replication fork, one strand is synthesized away from the replication fork, and one strand is synthesized toward the replication fork. When you look at both replication forks, note that a single new strand is built in the same direction on both sides of the replication bubble.

leading strand: made continuously, only one primer needed, daughter strand elongates toward replication fork

lagging strand: made in segments, multiple primers needed, daughter strand elongates away from the replication fork

both strands: synthesized 5' to 3'

Because DNA polymerase III can only add nucleotides to the 3' end of a new DNA strand and because the two parental DNA strands are antiparallel, synthesis of the leading strand differs from synthesis of the lagging strand.
The leading strand is made continuously from a single RNA primer located at the origin of replication. DNA pol III adds nucleotides to the 3' end of the leading strand so that it elongates toward the replication fork.
In contrast, the lagging strand is made in segments, each with its own RNA primer. DNA pol III adds nucleotides to the 3' end of the lagging strand so that it elongates away from the replication fork.
In the image below, you can see that on one side of the origin of replication, a new strand is synthesized as the leading strand, and on the other side of the origin of replication, that same new strand is synthesized as the lagging strand. The leading and lagging strands built on the same template strand will eventually be joined, forming a continuous daughter strand.

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What is the main reason for there being both a leading strand and a lagging strand during DNA replication?

What do leading and lagging strands have in common?

Why does the lagging strand lag behind the leading strand?