DNA replication

DNA stands for Deoxyribonucleic Acid. It is found in the chromosomes. It is responsible for the development, growth, and reproduction of an organism. They are very large molecules that are made up of several nucleotides. 

The diagram of a DNA structure looks like a twisted ladder. The rungs are made up of nitrogenous complexes. These nitrogenous complexes are helped together by hydrogen bonds. 

The side rails of this DNA ladder are called chains. The two chains and the rungs are opposites of each other. 

A single nucleotide unit consists of a nitrogen base. That nitrogen base is broken down into cytosine, guanine, adenine, and thymine. Guanine is paired with cytosine, while adenine is paired with thymine. When they make up a rung, guanine is always placed opposite cytosine and adenine is placed opposite thymine. They are never switched. If there is a switch then it is a mistake during DNA replication and DNA synthesis. It can lead to mutation and life-threatening diseases. 

Now that we have understood what DNA is, let us look at DNA replication.

DNA replication

DNA replication is the process whereby a double-stranded DNA molecule is copied so that it can produce two identical DNA molecules like itself.

DNA replication is a very simple process. It happens so that there will be the inheritance of traits by the offspring. Without DNA replication, the cells in the body will die leading to the death of the organism. 

DNA replication takes places like this:  Through cell division, a stage in the cell cycle, the DNA can replicate itself. To replicate means to multiply the exact thing. When the cell divides, the DNA strand breaks. Remember that the rings of the DNA ladder are made of nitrogenous complexes. These nitrogenous bases are held in place by hydrogen bonds. The hydrogen bonds are weak. This allows the DNA ladder to divide and the cell divides.

Initiation, Elongation, and Termination: 

The process where two replication forks are formed at the origin because the proteins bind to the origin of replication as helicase unwinds the DNA helix is known as initiation. It is followed by adding a primer sequence to the complementary RNA nucleotides. The process of the replacement of these by DNA nucleotides is known as the elongation. Termination refers to the condition when the primers are replaced with fresh DNA nucleotides after removing them.  The backbone is finally sealed by the DNA ligase.

Different Enzymes Involved: 

The enzymes involved during DNA replication are polymerase, DNA primase, DNA helicase, DNA ligase, and topoisomerase.

When the DNA ladder has divided, some of the nucleotides are free. These nucleotides then rearrange themselves with the broken half strands. The half strands are the chains of the ladder. 

When the nucleotides have arranged themselves, hydrogen bonds then go to hold the new ladders in place. Then you have two new DNA ladders that are identical. 

DNA synthesis

After DNA replication, we have DNA synthesis. During DNA replication, DNA synthesis is also carried out. DNA synthesis is the creation of new DNA either naturally or artificially. During DNA replication, when the strands break, they serve as new rungs of a new DNA ladder. That is what DNA synthesis is all about.

Types of DNA synthesis

 There are two types of DNA synthesis. They are:

• Vitro DNA replication: this can be done artificially in a laboratory. To carry out a vitro DNA replication, you need to separate the DNA polymerases from the cells. Then you take artificial primers, to serve as the chains for the DNA ladder.
• Vivo DNA replication: this happens in all living organisms. It is just as explained above.

What are prokaryotes?

Prokaryotes (you can also spell it as procaryotes) are organisms without internal membranes. It is so small that you need a microscope to see it. It has a single cell and those do not have a prominent nucleus. It also lacks vital organs. 

Remember that DNA is found in the chromosomes and the chromosomes are in the nucleus. How does the prokaryote replicate its DNA? 

DNA replication in prokaryotes

The process for DNA replication in prokaryotes is different from the one we have studied above. The method above can be found in animals and humans. 

The prokaryotes have a bacteria in them called E. coli. This bacteria, E. coli, has over 4 million base pairs in a single chromosome. Every single base pair can be replicated in less than 50 minutes. 

Prokaryotes use many enzymes during their replicating process. One of the enzymes is DNA polymerase. It is also used in human DNA replication. The work of the DNA polymerase enzyme is to add nucleotides to the chain as it grows. 

Aside from enzymes, energy is needed for the DNA replication process in prokaryotes. The energy is sourced from nucleotides that have three phosphates attached to them. 

These phosphates are in bonds and when the bonds holding them together break, a bond called phosphodiester is used to hold the next nucleotide to the chain. And that is how it continues.

During the DNA replication in prokaryotes, three enzymes are used. They are DNA pol I, DNA pol II, and DNA pol III. DNA pol I and II are needed for repairs if the chain should be damaged. DNA pol III is used for DNA synthesis in prokaryotes. 

Conclusion

It is now clear that DNA means Deoxyribonucleic Acid. A DNA ladder has rungs that are made up of nucleotides. DNA replication is the creation of exact copies of an already existing DNA ladder. DNA synthesis is the creation of new nucleotides during DNA replication. Prokaryotes are tiny organisms without a distinct nucleus and important organs. It uses three important enzymes during DNA replication: DNA pol I, DNA pol II, and DNA pol III. The first two are used for repairs while the last is used for DNA synthesis.