Sushiksha

Did you just move your finger to reach this particular page? Yes! Do you know that it takes so many proteins for this to happen? There are millions of such proteins in your body at the moment. Many of which do not last long. If that's the case, how does the body manage to survive? There's an entire pathway that all living organisms follow. This is known as the Central Dogma of Biology. 

In simpler terms, Central Dogma is the flow of information that the organism has at the genetic level. It's unidirectional (With a few exceptions). For a very long time, scientists believed that proteins are the genetic material in a living organism. After lots of hard work, it was proved that DNA serves as the genetic material and gives rise to proteins. This happens through three basic steps; that make the Central Dogma of Biology. These three steps are Replication, Transcription, and Translation. 

Replication
This is the most basic yet important step of gene transfer. For a cell to divide, the basic necessity is to have genetic material and replication is how a cell does that. It is just creating a duplicate of the DNA that you already have in you. One specialty of DNA is that it is semi-conservative. That means double-stranded DNA can synthesize another copy independent of each other. This creates 2 sets of DNA that can be passed on to the next cell. By this, DNA ensures that no information it has is either lost or missed in the next generation. 

Transcription
Transcription is another process through which a sequence of RNA strand is synthesized. RNA is DNA with a lack of oxygen atom at their 2nd position. In prokaryotes(organisms that lack a nuclear membrane and other primary organelles, the RNA synthesized straight away serves as the template for protein genesis and is termed mRNA( m stands for messenger). While in Eukaryotes( the advanced beings), it is quite complex. The DNA is transcribed to RNA but it will further undergo a lot of modifications such as capping, tailing, and slicing. It is only after this that the RNA is mature mRNA. 
In some cases, such as in retroviruses, a strange way of transcription happens in reverse order. i.e, RNA is reverse transcribed to form DNA. 

Translation
Once we have the mature mRNA, the only step left out is its usage. Protein synthesis is more like a computer program. The sequence on the mRNA is read; The necessary tRNA( used for transfer) is made to fetch the amino acid; All of this happens simultaneously inside a small unit called the ribosome. Once a chain of the polypeptide is formed, it further undergoes modifications giving it proper three-dimensional stability and a function to perform. 

This is how the information in a cell is passed and transferred within and to a new generation. The flow is always DNA -> RNA -> Protein. But there are definitely a few exceptions. Retroviruses as mentioned before are an exception for the Central Dogma. Apart from this, RNA to RNA is also observed in a few cases that lead to gene silencing; DNA to Protein without RNA is observed in certain in-vitro conditions. We also have a very strange organism called prions whose flow of information is yet unknown to the scientific world.