Question

Distinguish between (a) unidirectional and bidirectional synthesis, and (b) continuous and discontinuous synthesis of DNA.

Short answer

#Answer# The differences between unidirectional and bidirectional synthesis are that in unidirectional synthesis, DNA replication proceeds in only one direction, while in bidirectional synthesis, replication goes in both directions, making it more efficient. Continuous and discontinuous syntheses refer to the process of new complementary strand synthesis during DNA replication. Continuous synthesis occurs in the same direction as the replication fork movement, whereas discontinuous synthesis happens in the opposite direction, creating short Okazaki fragments which must later be joined together, making it slower and less efficient.

Step-by-step solution

Understanding Unidirectional and Bidirectional Synthesis

In unidirectional synthesis, DNA replication proceeds in only one direction from the origin of replication. In contrast, bidirectional synthesis involves replication going in both directions from the origin of replication, utilizing two replication forks.

Comparing Unidirectional and Bidirectional Synthesis

Unidirectional synthesis is less efficient as it takes more time for complete replication of the DNA, whereas bidirectional synthesis is more efficient as it allows for faster DNA replication by utilizing two replication forks moving in opposite directions.

Understanding Continuous and Discontinuous Synthesis

During DNA replication, the two strands are separated and serve as templates for the synthesis of new complementary strands. Continuous synthesis occurs when the new strand is synthesized in the same direction as the replication fork movement. Discontinuous synthesis happens when the new strand is synthesized in the opposite direction to the replication fork movement, creating short fragments called Okazaki fragments.

Explaining Leading and Lagging Strand

In DNA replication, the two template strands are called the leading strand and the lagging strand. The leading strand is the one where continuous synthesis takes place, with the new strand being synthesized in the same direction as the replication fork movement. The lagging strand undergoes discontinuous synthesis, creating short Okazaki fragments which are later joined to form a continuous strand.

Comparing Continuous and Discontinuous Synthesis

Continuous synthesis is faster and more efficient as it is performed in the same direction as the replication fork movement and is synthesized as a single, continuous strand. Discontinuous synthesis, on the other hand, is slower due to the formation of Okazaki fragments which must later be joined together, requiring an extra enzyme and an additional energy-consuming step.