Which portion of a chromosome contains Okazaki fragments? a. helicase b. lagging strand c. leading strand d. primer
The correct answer and explanation is:
The correct answer is b. lagging strand.
During DNA replication, the two strands of the DNA double helix are unwound, and each serves as a template for the formation of a new complementary strand. The process of replication occurs in a semi-discontinuous manner, meaning that while one strand is synthesized continuously, the other is synthesized in fragments.
The leading strand is synthesized continuously in the 5′ to 3′ direction, following the direction of the replication fork. This is because the DNA polymerase can add nucleotides in the same direction as the unwinding of the DNA.
On the other hand, the lagging strand is synthesized discontinuously because DNA polymerase can only add nucleotides in the 5′ to 3′ direction. As the replication fork moves, the lagging strand is oriented in the opposite direction, so it must be synthesized in short segments called Okazaki fragments. These fragments are eventually joined together by the enzyme DNA ligase to form a continuous strand.
The synthesis of the lagging strand begins with the formation of a primer, a short RNA sequence synthesized by the enzyme primase, which provides a starting point for DNA polymerase to begin adding nucleotides. Okazaki fragments are formed by repeated cycles of primer addition, DNA polymerase activity, and ligation, making them a characteristic feature of the lagging strand during DNA replication.
In summary, Okazaki fragments are found on the lagging strand, where DNA replication is more complex due to the opposing directionality of the strand relative to the replication fork.