The central dogma of molecular biology describes the two-step process properly viz. transcription and translation, by which the information in genes flows into proteins: (DNA → RNA → Protein).
The Central Dogma Model was stated by Francis Crick in 1957 and then published in the year 1958.
The importance of Central Dogma is a huge contribution to Modern Biology. It brought light to the mechanisms governing the specification and transmission of genetic traits that were understood properly for the first time only after its discovery.
Central Dogma Model shows the basic framework showcasing the flow of genetic information from DNA sequence to the proteins thus bringing adequate changes to the living body.
The central dogma of molecular biology deals with the detailed residue-by-residue transfer of sequential information during gene expression.
It is via this model that showcases how the genes of a living body are expressed by so-called gene expression.
There’s so much importance of this model to molecular biology. Let’s know about it!
So, keep reading...
- The Importance Of The Central Dogma To Modern Biology. Check These Out:
- 1. In the 20th century, the mechanisms governing the specification and transmission of genetic traits were understood for the first time
- 2. It proves the genetic nature of DNA and not the proteins
- 3. It explains the flow of genetic information from DNA to mRNA
- 4. It explains the flow of genetic information from mRNA to Proteins
- 5. In retrovirus, it is partially helpful in explaining the flow of genetic information
- 6. It shows that genetic information cannot be transferred among proteins, or from proteins to nucleic acids
- 7. It brought light to the discovery of codons coding for the various amino acids
- 8. It brought light to the stability of the DNA helical structure during genetic expression
- 9. It brought light to the semi-conservative model of DNA replication
- 10. It brought light to the idea of DNA packaging
- 11. It also describes the process of molecular evolution by which self-organizing systems can develop
The Importance Of The Central Dogma To Modern Biology. Check These Out:
1. In the 20th century, the mechanisms governing the specification and transmission of genetic traits were understood for the first time
Before the introduction of the Central Dogma Model, not everyone accepted that nucleic acids were involved in protein synthesis.
Earlier it was not so genetically clear about the concept of molecular evolution in the ancestral pedigree analysis.
The other central problems of molecular biology that includes those of gene action and nucleic acid synthesis were also not so cleared.
In fact, scientists didn’t even know the function and composition of ribosomes. Not even the presence of tRNA and mRNa was known with proper scientific evidences.
Nobody knew perfectly what actually was in a gene and what took place if DNA was used as a template for RNA.
Crick showed that there is a huge relation between DNA, RNA, and proteins.
Thus, the introduction to the Central Dogma of Biology showed the mechanisms governing the specification and transmission of genetic traits for the first time.
It showed how DNA acts as a template to create an intermediate RNA, and then how the base sequence of RNA forms the proteins expressing the genetic traits.
This highlighted the existence of a link between the base sequences of nucleic acids and those of amino acids in a protein. Thus, it also highlighted the reality of the genetic code.
2. It proves the genetic nature of DNA and not the proteins
Crick’s main concept was to explore rich evolutionary sources of information by comparing sequence data of the DNA.
The central Dogma Model showed that DNA is composed of a polynucleotide chain which has sequential nitrogenous bases that contain the genetic information of an organism.
This DNA is the genetic material in our cells and it has been derived from our biological parents and determines that many of our characteristics are similar to our parents.
Proteins are not derived from our parents but produced of its own in everyone’s body. They don’t carry any heritable information between generations.
This DNA has sequential genetic information that can express itself in some way or the other to bring various genetic traits. These genetic traits can determine your eye color, facial features, and other physical attributes.
So, the DNA is actually the genetic information storehouse proving the genetic nature of DNA. And proteins are formed from DNA whenever required.
The discovery that DNA as genetic material and not the proteins is another important milestone in molecular biology.
3. It explains the flow of genetic information from DNA to mRNA
This model states the flow of genetic information from DNA to mRNA. This is also known as Transcription, which is the process by which the information in a strand of DNA is copied into a new strand of messenger RNA (mRNA).
The central dogma model shows that DNA has the genetic information coded in its sequential bases. Those sequential bases can bring out the genetic traits in the body but through a series of molecular steps.
In that series of steps, the DNA has to be converted into mRNA (messenger RNA) strand. This mRNA will act as some kind of intermediate between DNA and formation of proteins.
Thus, mRNA will only act as a messenger between DNA and protein formation. This mRNA stores the information on how to code for proteins.
DNA cannot leave the nucleus, so the mRNA is formed from DNA. Additionally, this mRNA can leave the nucleus.
Through mRNA, the DNA is able to transmit its messages out to other parts of the cell.
DNA will act just like a storehouse of genetic information. The mRNA will act as an easily readable form of the genetic information derived from the DNA.
4. It explains the flow of genetic information from mRNA to Proteins
This model also states the flow of genetic information from mRNA to the amino acid sequence of polypeptide forming the proteins. This is also known as Translation.
The mRNA that was formed from DNA is very short-lived so, it has to be converted to some form. So in order to do so, mRNA attracts ribosomes.
Ribosomes are proteins that read messages in the mRNA and convert them into a string of amino acids (the basic building blocks of proteins).
The role of the ribosomes here is just to decode the message stored in the mRNA and transfer it to tRNA (transfer RNA). That tRNA transfers amino acids to a newly forming protein.
A long chain of amino acids emerges as the ribosome decodes the mRNA sequence into a polypeptide or a new protein.
Molecules of tRNA are responsible for matching amino acids with the appropriate codons in mRNA.
Thus, you can say that tRNA is the transfer vehicle which is very important for the flow of genetic information from mRNA to Protein.
5. In retrovirus, it is partially helpful in explaining the flow of genetic information
In some viruses (retroviruses) the flow of information is in reverse direction i.e from RNA to DNA. This is called the central dogma reverse model.
RNA of these viruses first synthesizes DNA in the presence of Reverse Transcriptase enzyme. DNA then transfers information to RNA and the translation occurs.
That’s why it is said that in retrovirus, the central dogma model is partially (not-fully) helpful in explaining the flow of genetic information.
RNA in biological cells is just a single-stranded molecule. The 2′-hydroxyl group on the pentose ring makes RNA less stable than DNA because it becomes more susceptible to hydrolysis.
But in retroviruses, it was seen that the RNA contains genetic information but is not able to create proteins to show the genetic traits. So, the presence of RNA makes the virus non-living.
So, if the retrovirus enters a host cell it becomes living and can create a DNA pro-virus by reverse transcription.
That DNA pro-virus can replicate and form an mRNA in the host cell which will later translate to proteins.
6. It shows that genetic information cannot be transferred among proteins, or from proteins to nucleic acids
According to the central dogma model, neither DNA nor RNA, but the proteins are the only final product that will bring in the genetic traits in the living body.
The ‘central dogma’ of molecular biology states that sequence information can be transferred among nucleic acids (DNA & RNA), and from nucleic acids to proteins, but sequence information cannot be transferred among proteins, or from proteins to nucleic acids.
DNA acts as the storehouse of genetic information, RNA takes the genetic message of the DNA and translates it to Proteins.
Thus, proteins become those biomolecules that will bring the results (genetic traits) of that genetic information that was stored in DNA.
Every protein type with a known amino acid sequence is different and serves a different purpose.
The finally produced proteins are consumed by the cells to showcase the genetic traits. So, the process of formation of proteins goes on as the cells actively consume it for its various needs.
So, that’s why the central dogma model is only a one-step process and not a cyclic process. This shows that genetic information cannot be transferred among proteins, or from proteins to nucleic acids.
7. It brought light to the discovery of codons coding for the various amino acids
The relationship between the sequence of amino acids in a protein polypeptide chain and the nucleotide sequence of mRNA is called Genetic code. A genetic code consists of 64 codons.
During the time of translation (protein synthesis) from mRNA to proteins, the tRNA reads the mRNA based on a particular sequence of three nucleotides and then creates the amino acids respectively. A protein is a huge polypeptide chain of amino acids.
Each codon consists of three nucleotides, usually corresponding to a single amino acid. For example, the codon CAG represents the amino acid glutamine.
The nucleotides are abbreviated with the letters A (Adenine), U (Uracil), G (Guanine), and C (Cytosine).
Thus, the discovery of codons coding for the various amino acids is possible after researching a lot about the translation step of the Central Dogma Model.
Thus, it can be stated that the central dogma model brought light into the discovery of codons coding for the various amino acids.
8. It brought light to the stability of the DNA helical structure during genetic expression
During the gene expression, that is the transcription of DNA to mRNA and then the translation of mRNA to Proteins according to Central dogma shows that DNA structure is very stable.
The structure of the DNA helix is stabilized by Van-der-waals forces, hydrogen bonds between complementary organic bases (a base pair), and hydrophobic interactions between the nitrogenous bases and the surrounding sheath of water.
The structure of DNA is very stable than that of the RNA. The DNA is double helix in structure and the RNA is single-stranded.
This stability is important because it prevents the two DNA strands from breaking apart spontaneously and plays an important role in the way DNA is copied.
Due to its stable structure DNA cannot be broken down very easily. So, replication of DNA occurs in a semi-conservative way using energy from ATP.
After the replication, the mRNA strand is produced from a single DNA strand for proper transcription to take place.
So, RNA due to its less stability makes it possible for the easy and proper translation of proteins whenever the living organism needs it.
9. It brought light to the semi-conservative model of DNA replication
The semi-conservative model of DNA replication shows that the two original DNA strands separate during replication and, each strand then serves as a template for a new DNA strand.
During transcription, only one strand of DNA acts as a template for RNA synthesis.
Thus, this separation of the two stable strands of DNA is very necessary or else transcription won’t take place.
Else if, semi-conservative replication of DNA wouldn’t have been taken place then both the strands of DNA would have been coding for RNA, which would have created double-stranded RNA.
This double-stranded RNA would have been prevented from being translated into proteins thus making the translation more futile.
10. It brought light to the idea of DNA packaging
Do you know how long the DNA strand is? There are a total of 3 billion base pairs in each cell’s DNA which is about 2m long. All the DNA in all your cells put together would be about twice the diameter of the Solar System.
In prokaryotic cells, DNA is supercoiled, meaning that the DNA is either under-wound or over-wound from its normal relaxed state.
In eukaryotic cells, DNA is wrapped around proteins known as histones to form structures called nucleosomes.
So, such lengthy DNA is tightly twisted, turned, compressed, and then packed to fit in the nucleus of every cell.
How? It’s packed into nucleosome which is further compressed and packed to fit the size of a chromatid fiber.
During replication of DNA and then for transcription, DNA has to be un-twisted, un-turned, un-compressed, and then un-packed using energy.
If such a thing doesn’t occur the formation of RNA cannot take place and so no protein formation will occur as well.
Thus, the Central Dogma model also brought light into this matter making it more precisely understandable.
11. It also describes the process of molecular evolution by which self-organizing systems can develop
Self-organizing systems are the living systems that know how to genetically provide support for its own sustainability by taking its own genetic information to carry on its own body physiological and metabolic activities. Genetic information are all stored in DNA.
According to the central dogma, DNA directs its own replication and its transcription to yield RNA which, in turn, directs its translation to form proteins.
The information on how, where, when, and why to do gene expression is all stored in DNA as well.
And the DNA contains all the information that the organisms have learned and developed over the course of its evolution from time to time.
All the evolutionary changes are recorded in the DNA which is getting transferred generation after generation from parents to offsprings.
So, how evolutionary information is getting passed generation after generation leading to the present day self-organizing living organisms?
Well, it’s all how the central dogma model proves how the genetic traits have been passing generation after generation with mutations. And how these traits are expressing themselves from DNA to RNA to Proteins.