Final answer:
DNA replication occurs in the 5' to 3' direction. The leading strand is synthesized continuously, while the lagging strand is synthesized in Okazaki fragments, also in the 5' to 3' direction. No synthesis occurs in the 3' to 5' direction.
Step-by-step explanation:
In the process of DNA replication, nucleotides can only be added in the 5' to 3' direction. This is due to the enzyme DNA polymerase, which facilitates the addition of nucleotides to the growing DNA chain.
As DNA strands are anti-parallel, one strand (the leading strand) can be synthesized continuously in the direction of the replication fork, while the other (the lagging strand) requires synthesis in short segments called Okazaki fragments, which are also synthesized in the 5' to 3' direction but away from the replication fork.
Thus, to answer the original question, DNA replication takes place in the 5' to 3' direction, and it does not go in the 3' to 5' direction.
The direction in which DNA synthesis occurs is from the 5' to the 3' end. The 5' end refers to the phosphate group attached to the 5th carbon of the deoxyribose sugar in DNA, while the 3' end refers to the hydroxyl group attached to the 3rd carbon. This directionality is due to the specific structure of DNA with its antiparallel strands.