what are the three steps of DNA replication?
The Correct Answer and Explanation is:
Correct Answer:
The three steps of DNA replication are initiation, elongation, and termination.
Explanation
DNA replication is a fundamental process that occurs in all living organisms to ensure that each new cell receives an exact copy of the genetic material. The process takes place during the S phase of the cell cycle and is composed of three main steps: initiation, elongation, and termination.
The first step, initiation, begins at specific regions in the DNA called origins of replication. In this step, certain proteins recognize these origins and bind to them, causing the DNA to unwind and form a replication bubble. Enzymes like helicase help in unwinding the double helix by breaking the hydrogen bonds between the complementary base pairs. Single-strand binding proteins then attach to the separated strands to keep them apart, allowing them to serve as templates for new DNA synthesis. Another important enzyme, primase, synthesizes a short RNA primer that provides a starting point for DNA synthesis.
The second step, elongation, involves the synthesis of new DNA strands. DNA polymerase adds new nucleotides to the growing strand in a sequence complementary to the template strand. It can only add nucleotides in the 5′ to 3′ direction. On the leading strand, synthesis occurs continuously toward the replication fork. On the lagging strand, synthesis is discontinuous and occurs in short fragments known as Okazaki fragments. These fragments are later joined together by the enzyme DNA ligase.
The final step, termination, occurs when replication is complete. The replication forks meet, and the newly formed strands are separated from each other. Any remaining RNA primers are removed and replaced with DNA. The fragments on the lagging strand are joined to form a continuous strand. At this point, two identical DNA molecules are formed, each containing one original strand and one new strand. This method of replication is called semiconservative because each new molecule conserves one original strand.
