DNA Replication Overview

The process of copying DNA, essential for cell division and the transfer of genetic material.

Replication that results in each new DNA molecule containing one original strand and one newly synthesized strand.

Sections of the genome that are replicated independently, allowing for faster and coordinated DNA synthesis.

The starting point for DNA replication on a replicon.

The point where the DNA double helix is being unwound and new DNA strands are being synthesized.

DNA polymerase III extends the lagging strand by adding deoxynucleotides to RNA primers. The lagging strand is looped to allow two DNA polymerases to work simultaneously.

DNA polymerase III detaches from the lagging strand after encountering a previously synthesized Okazaki fragment.

DNA polymerase III attaches to the lagging strand template further along its length and starts elongating from the next RNA primer. This process continues until it reaches the previously synthesized Okazaki fragment.

DNA polymerase I removes RNA primers of the Okazaki fragment by exonuclease activity (5'→3') and fills the gap with deoxyribonucleotides.

DNA ligase joins the newly synthesized DNA fragments (Okazaki fragments) together, forming a continuous strand.

The leading strand is continuously synthesized towards the replication fork, while the lagging strand is synthesized discontinuously in smaller fragments called Okazaki fragments, growing away from the fork.

A new strand of DNA is always synthesized in the 5' to 3' direction, adding nucleotides to the 3' end.

The enzyme responsible for unwinding the DNA double helix during replication, breaking the hydrogen bonds between the bases, using energy from ATP hydrolysis.

Proteins that bind to single-stranded DNA, preventing it from re-annealing, ensuring the template strands stay separated during replication.

Small RNA segments synthesized by primase, providing a starting point for DNA polymerase to bind to the template, creating a 3' end to add nucleotides to.

A complex of proteins that binds to the origin of replication in eukaryotic cells, initiating the replication process.

A complex formed at the origin of replication in eukaryotic cells, consisting of ORC, licensing factors, and helicase, ultimately leading to the activation of DNA replication.

Type II topoisomerases break and rejoin double-stranded DNA to change DNA topology, introducing or removing supercoils. This process requires ATP and is crucial for untangling and separating DNA strands, especially during replication and cell division.

DNA gyrase is a specific type II topoisomerase found in bacteria. It introduces negative supercoils into DNA, which helps to compact the molecule and make it more accessible for replication and transcription.

The DNA polymerase III holoenzyme is a complex protein machine responsible for DNA replication in prokaryotes. It consists of two core DNA polymerase III enzymes, which replicate the DNA, multiple beta clamps that hold the polymerase to the DNA, a gamma clamp loading complex that helps attach the clamps, and a helicase that unwinds the DNA.

The beta clamp is a ring-shaped protein that encircles the DNA and keeps the DNA polymerase III enzyme attached to the DNA strand during replication. This allows the polymerase to continuously synthesize DNA without falling off.

The replisome is the entire complex of proteins that work together at the replication fork to copy DNA. It includes the DNA polymerase III holoenzyme, the helicase, single-stranded DNA binding proteins, and primase.

Helicase is an enzyme that unwinds the double-stranded DNA helix during replication. It uses ATP energy to break the hydrogen bonds between the DNA bases, creating a replication fork.

Primase is an enzyme that synthesizes short RNA primers on the lagging strand during DNA replication. These primers provide a starting point for DNA polymerase III to begin DNA synthesis.

The lagging strand is the strand of DNA that is synthesized discontinuously during replication. It is synthesized in short fragments called Okazaki fragments, which are later joined together.

The leading strand is the strand of DNA that is synthesized continuously during replication. It is synthesized in the same direction as the replication fork movement.

Okazaki fragments are short DNA fragments that are synthesized on the lagging strand during replication. They are later joined together by DNA ligase to form a continuous DNA strand.