Question

Label the leading and lagging strands in the last picture. Explain what is meant by the “lagging” strand and why this occurs

Answer 1

The leading strand is synthesized continuously in the 5' to 3' direction, while the lagging strand is synthesized in short segments in the opposite direction. This occurs because DNA polymerase can only add nucleotides in the 5' to 3' direction. The lagging strand synthesis is more complex and involves the use of primers for each segment.

Step-by-step explanation:

The leading and lagging strands in DNA replication are synthesized in opposite directions. The leading strand is the strand that is continuously synthesized in the 5' to 3' direction as the replication fork moves. On the other hand, the lagging strand is synthesized in short segments called Okazaki fragments in the 5' to 3' direction, which is opposite to the direction of the replication fork.

This occurs because DNA polymerase, the enzyme responsible for building new DNA, can only add nucleotides in the 5' to 3' direction. To begin synthesis, DNA polymerase requires a primer, which is built by the enzyme primase. The leading strand can be extended continuously from a single primer, while the lagging strand needs a new primer for each Okazaki fragment.

Overall, the lagging strand synthesis is more complex and requires additional steps compared to the leading strand, resulting in its 'lagging' nature.

Answer 2

Step-by-step explanation:

Leading Strand:

The leading strand is synthesized continuously in the 5' to 3' direction, which is the same direction as the movement of the replication fork.

DNA polymerase can synthesize this strand in a continuous manner by adding nucleotides in the direction of the replication fork.

It's called the "leading strand" because it leads the replication process in the same direction as the replication fork movement.

Lagging Strand:

The lagging strand is synthesized discontinuously in the 3' to 5' direction, which is opposite to the movement of the replication fork.

DNA polymerase synthesizes this strand in short fragments called Okazaki fragments.

These fragments are later joined together by DNA ligase to form a continuous strand.

It's called the "lagging strand" because it lags behind the replication fork as it is synthesized in the opposite direction.