Question

In DNA replication, the new strand always grows in which direction?

1) 5' to 3' direction
2) 3' to 5' direction
3) Both 5' to 3' and 3' to 5' directions
4) Cannot be determined

Answer 1

The new strand in DNA replication grows in the 5' to 3' direction, with the leading strand synthesized continuously and the lagging strand synthesized in Okazaki fragments.

Step-by-step explanation:

In DNA replication, the new strand always grows in the 5' to 3' direction. This is because DNA polymerases are enzymes that can only add nucleotides to the 3' end of the growing DNA strand. Consequently, DNA synthesis always progresses by adding new nucleotides to the 3' end of the nascent strand. The strand that is synthesized in a continuous manner toward the replication fork is known as the leading strand. Conversely, the strand that grows away from the replication fork does so discontinuously, forming Okazaki fragments, and is called the lagging strand. Each Okazaki fragment starts with a primer and grows in the 5' to 3' direction until it reaches the preceding fragment, after which a DNA ligase joins the fragments together. All of this illustrates the importance of directionality in DNA replication and the 5' to 3' growth of new DNA strands.