Enzymes Involved in DNA Replication

Most likely, DNA replication is one of the most amazing things it can do. If you think about it, each cell has all the DNA it needs to make the other cells. And we start with a single cell and end up with trillions of cells. During this process, all of the information in a cell has to be copied perfectly. So DNA is a molecule that can be copied to make copies that are almost as good as the original. Even more amazing when you consider that there are almost 3 billion base pairs of DNA to copy. And replication is done with the help of DNA polymerases, which are molecules that only copy DNA. All of the DNA in a single human cell has to be copied over and over again, which takes several hours. At the end of this process, when all of the DNA has been copied, the cell has twice as much DNA as it needs. It can then divide and give some of this DNA to the daughter cell, so that the daughter cell and the parent cell are often exactly the same genetically.

DNA Replication

 DNA replication is a semiconservative process in which each parent strand acts as a template for making a new daughter strand that is complementary to it. DNA polymerase is the most important enzyme which helps in extending the  complementary strand . It helps the deoxyribonucleoside 5′-triphosphates (dNTPs) join together to make the growing DNA chain. DNA replication, on the other hand, is much more complicated than a single enzyme reaction. There are also other proteins involved, and mechanisms for checking for mistakes are needed to make sure that the accuracy of replication is in line with the low number of mistakes that are needed for cell reproduction. To start replication and copy the ends of eukaryotic chromosomes, you also need extra proteins and certain DNA sequences.

The Mechanism of DNA Replication

There are three main steps in the process of DNA replication.

1. The opening of DNA’s double-helix structure and the splitting of its two strands
2. Giving the template strands a head start
3. Putting the new pieces of DNA together

• When DNA is split in two, the two strands unwind at a place called the origin. With the help of a number of enzymes and proteins, they get the strands ready to be copied
• At the end of the process, an enzyme called DNA polymerase starts putting together the new DNA strands
• These are the general steps that all cells go through when they copy their DNA. However, depending on the organism and type of cell, these steps can be different
• Enzymes are very important to DNA replication because they speed up some of the most important steps
• DNA replication is one of the most important parts of how a cell works, so a lot of research has been done to figure out how it works
• The process of DNA replication in Escherichia coli is well understood. This process is also the same in eukaryotic cells
• In E.coli, DNA replication starts at the oriClocus (oriC), which is where the DnaA protein binds while ATP is being broken down

DNA replication enzymes and Proteins

The enzyme DNA polymerase

• DNA polymerases are enzymes that make DNA by adding nucleotides to the growing DNA chain one at a time. The enzyme adds amino acids that match the ones in the template strand
• Both prokaryotic and eukaryotic cells have DNA polymerase. They both have a number of different DNA polymerases that do different jobs in the replication and repair of DNA

DNA Helicase enzyme

• This is the enzyme that helps unwind the double-helix shape of DNA, which makes it possible for DNA replication to start
• It breaks the hydrogen bond between the DNA bases and separates the strands by using the energy released when ATP is broken down
• This causes each separated strand to have two replication forks that go in different directions
• At each replication fork, the parental DNA strand must unwind, revealing new sections of single-stranded templates
• The helicase enzyme unwinds the strands in a precise way that doesn’t change the shape of the DNA molecule

DNA primase enzyme

• This is a type of RNA polymerase enzyme that is used to make RNA primers, which are short pieces of RNA that start the process of DNA replication

DNA ligase enzyme

• This is the enzyme that makes phosphodiester bonds between nucleotides, which are the building blocks of DNA

Exonuclease

• These are a group of enzymes that take nucleotide bases off the end of a DNA chain

Topoisomerase

• This is the enzyme that gets rid of the topological stress that happens when a molecule unwinds
• They cut one or both strands of DNA, which lets the strands move around each other and release tension before the ends come back together
• Because of this, the enzyme speeds up the breakage it causes by putting the broken strands back together
• In E. coli, topoisomerase is also called DNA gyrase

Telomerase

• This enzyme is found in eukaryotic cells. It adds a specific sequence of DNA to the telomeres of chromosomes after they divide. This keeps the chromosomes stable over time

Conclusion

Replication is important because when a cell divides into two, the two new cells must have the same DNA, or genetic information, as the parent cell. The process of duplication is based on the fact that each strand of DNA can be used as a model.