Replicación de ADN

Overview of DNA Replication

This section provides a general introduction to DNA replication and its semi-conservative nature.

DNA Replication Process

• DNA replication is semi-conservative, with each parental strand acting as a template for the synthesis of a new complementary strand.

• The process starts by unwinding the DNA and breaking hydrogen bonds between the two strands. Single-strand binding proteins (SSBs) prevent reannealing, creating a replication bubble.

• Multiple replication bubbles form along the DNA molecule, significantly increasing replication speed.

• The leading strand is synthesized continuously towards the replication fork in the 5' to 3' direction.

• The lagging strand is synthesized discontinuously away from the replication fork in Okazaki fragments.

• RNA primers are used to initiate synthesis on both strands, providing a free 3' end for DNA polymerase to bind and add nucleotides.

• Polymerization occurs as nucleotides are added and phosphodiester bonds are formed between them.

• The lagging strand is synthesized in short fragments called Okazaki fragments, which are later joined by ligase.

• The process continues until both strands have been fully replicated.

Conclusion

DNA replication involves unwinding the double helix, synthesizing new strands using existing ones as templates, and joining the fragments to create two identical DNA molecules.

Replication of Leading and Lagging Strands

This section focuses on the replication of the leading and lagging strands during DNA replication.

Leading Strand Replication

• The leading strand is synthesized continuously in the 5' to 3' direction towards the replication fork.

• Another leading strand is simultaneously replicated on the opposite side of the replication bubble.

Lagging Strand Replication

• The lagging strand is synthesized discontinuously in short Okazaki fragments away from the replication fork.

• A second lagging strand is present at the opposite end of the replication bubble.

• Each Okazaki fragment is synthesized by a different DNA polymerase, which replaces RNA primers with DNA nucleotides.

• Ligase seals the gaps between Okazaki fragments, completing lagging strand synthesis.

Conclusion

During DNA replication, both leading and lagging strands are replicated simultaneously but in different directions. The leading strand is synthesized continuously, while the lagging strand is synthesized discontinuously in fragments that are later joined together.

Summary

In summary, DNA replication is a semi-conservative process where each parental strand serves as a template for synthesizing new complementary strands. The process involves unwinding and separating the DNA strands, creating replication bubbles along with multiple sites for simultaneous replication. The leading strand is synthesized continuously towards the replication fork, while the lagging strand is synthesized discontinuously in short fragments called Okazaki fragments. RNA primers are used to initiate synthesis, and DNA polymerase adds nucleotides in the 5' to 3' direction. Ligase seals the gaps between Okazaki fragments, resulting in two identical DNA molecules.