The DNA although has the power but directly cannot bring the genetic traits in the living body. So, DNA has to depend on the formation of RNA as an intermediate, and this RNA will form the structure of the proteins.
The proteins are the final non-self-replicating products that are utilized or consumed by the body cells to show the various genetic trains that are present in the DNA.
Therefore, the flow of genetic information in cells is from DNA to RNA to Protein. That’s the Central Dogma of Biology.
But, How Is The Central Dogma Evidence For Evolution? The Central Dogma shows how DNA is the self-replicating genetic storehouse of any biological body that is derived from their ancestors. So, if you compare the DNA sequences of any organism you’ll find the evolutionary relationships between very different species over the course of evolution.
- How Is The Central Dogma Evidence For Evolution?
How Is The Central Dogma Evidence For Evolution?
The genome is actively protected
We all know that a gene is the basic physical and functional unit of heredity meaning that it passes the physical or mental characteristics genetically from one generation to another.
Genes are segments of DNA that code for a specific genetic trait in a living body. And, a genome is an organism’s whole complete set of DNA, including all of its genes.
So, the genome is very important as it has been carrying all of the information from generation and generation over the course of millions of years of evolution.
So, this genome is being actively protected by a variety of mechanisms over the course of evolution.
The molecular machines continually scan DNA, comparing the complementary strands to find copying errors and looking for damage caused by UV radiation, and chemical mutagens. When errors are found, they are cut out and corrected.
So, Why is the genome protected?
The genome is protected because it contains the hereditary genetic information of our ancestors who have evolved a lot to make living on this planet a lot easier.
And, if that genome is not protected those evolutionary changes won’t pass to the next generation and so the upcoming generation won’t have that genetic development and so can become extinct very soon.
How is the genome protected?
Just like self-replicating coding DNA, there’s also self-replicating non-coding DNA present in our body.
The non-coding DNA constitutes a shield of peripheral heterochromatin that physically protects the genome and the central protein-coding sequences from various physical and chemical effects.
The Central Dogma sets out a hierarchy of information
Previously we have learned that the genome of an organism is it’s complete set of DNA, and a single gene is a part of that whole genomic DNA that can bring a genetic change in the living body.
But, that DNA (part of the genome) is self-replicating and it passes to the next generation during reproduction, either sexually or asexually.
During, sexual reproduction that DNA first replicates itself and passes to the next generation via. gametogenesis following the process of meiosis.
In the case of asexual reproduction, that DNA passes to the next generation via. spores, or budding, or binary fission following the process of the mitosis.
So, when that DNA passes from generation to generation it has always been transferring the hierarchy of information since DNA is the genetic information store.
DNA can be replicated because both strands contain a complete set of information and both of the strands can act as templates for the generation of a daughter DNA double helix that is identical to the parent.
And DNA can be transferred because from generation to generation because of the reproduction process through mitosis and meiosis.
While in mitosis, DNA is generally transferred from one cellular generation to the next. And, in meiosis and subsequent sexual reproduction, DNA of both parents get mixed up and gets transferred.
This shows how the DNA replicates in the reproducing bodies and gets transferred to the next generation. In the next generation, that DNA brings the same genetic traits via. the model as showed in the central dogma framework.
It is supported by the Oparin-Haldane Hypothesis
If we talk about Pre-biotic chemistry we can know that life occurred from inorganic compounds due to the earth’s physical and chemical effects.
The theory of chemical evolution states the formation of organic molecules from inorganic ones. Oparin and Haldane proposed this theory which is also called a chemical theory.
This theory states that first life originated from pre-existing, non-living organic molecules like RNA, proteins, etc. by chemical evolution. i.e. the formation of organic molecules from inorganic ones.
This chemical theory is explained dedicatedly by the Oparin-Haldane hypothesis suggesting that life arose gradually from inorganic molecules, with building blocks of life like amino acids forming first and then combining to make complex polymers like proteins.
Stanley Miller and Urey experimentally proved the chemical evolution of life. They created conditions similar to the primitive atmosphere using glass apparatus and tubes in the library.
They observed a large number of organic molecules and some amino acids like alanine, glycine, aspartic acids, etc. to be formed during the experiment from inorganic molecules.
Thus, the Oparin-Haldane Hypothesis explains that the elements and molecules that were observed during the experiments are all present in the biomolecules like DNA, RNA, proteins, etc.
And the process of the Central Dogma Model is, directly and indirectly, is dedicated through the involvement of molecules like nucleotides, hydrogen, carbon, nitrogen, ammonia, etc. that are included in the gene expression process.
DNA is self-replicating
Yes, the DNA is self-replicating as stated by the Central Dogma of Biology.
The DNA that is derived from the offspring is just a few copies that can’t be directly transcribed and translated to proteins. So, in order to bring a whole lot of genetic traits in the whole body that DNA needs to be present in more than a few copies in each and every cells of the body.
So, how those few copies of DNA will produce more copies so that the proper transcription and translation take place? That can be done because of the self-replicating nature of DNA.
The self-replicating nature of the DNA means that DNA itself has the power and mechanism to replicate itself without the use of any external means. So, this comes handy during the process of gene expression.
If a self-replicating molecule like DNA were versatile enough, it might evolve the capacity to help itself even further by segregating or synthesizing its own building blocks.
The DNA might also catalyze the formation of auxiliary molecules e.g. proteins, that could assist in replication.
A self-replicating system of molecules must keep its components together, otherwise, they will lose the evolutionary advantage that they have gained by cooperating. They could be tethered together or physically contained – perhaps in the space enclosed by a lipid bilayer.
One advantage of in-vitro self-replicating systems is their simplicity just like the small DNA. This enables detailed analysis of the evolutionary process at a level impossible when using complex organisms.
This shows how the self-replicating process of DNA that is proposed in the Central Dogma Model is very important in understanding various evolutionary evidence.
At an early stage, life consisted of a self-replicating RNA system
It has been proposed that, at an early stage, life consisted of a self-replicating RNA system, and that DNA and proteins evolved later. This is in accordance with the RNA world hypothesis.
According to this RNA world hypothesis, simpler biopolymers came first and those evolved the ability to catalyze the production of RNA, which then took over the genetic control of the first formed simple living organisms.
Earlier that RNA was self-replicating and was a very stable-versatile compound in the ancestral first formed organisms and had the ability to control the genetic needs.
RNA had the capacity to help itself even further by segregating or synthesizing its own building blocks.
RNA was able to self-replicate and also able to catalyze the formation of various proteins but was non-living in nature.
In some present-day viruses (retroviruses), RNA is still the genetic compound as it was during the early days of evolution.
In retrovirus, the genetic flow of information is in reverse direction i.e from RNA to DNA.
RNA of the retroviruses first synthesizes DNA in the presence of Reverse Transcriptase enzyme. DNA then transfers information to RNA and the translation occurs. This is called the central dogma reverse model.
The presence of RNA makes the retroviruses still non-living. So, if the retrovirus enters a host cell it becomes living and can create a DNA pro-virus by reverse transcription mechanism.
That DNA pro-virus can replicate and form an RNA in the host cell which will later translate to proteins. And, those proteins can show the retroviral genetic traits in the host cell.
Mutation in accordance to Central Dogma
A gene mutation is a permanent alteration in the DNA base sequence, such that the sequence differs from what is found in most people or from its parents.
Mutations occur in very rare cases but, it does occur and had been occurring quite a few times during the course of evolution.
In rare cases, during a person’s life span there may be few cells where the mutation occurs.
These mutational changes can be caused by environmental factors such as UV from the sun, chemical factors, replication mistakes, or can occur if an error is made as DNA copies itself during cell division.
For example: In the human genome, there are over 3.1 billion bases of DNA, and each base must be faithfully replicated for cell division to occur. Mistakes, although surprisingly rare, do happen. And so about one in every 1010 (10,000,000,000) base pair is changed due to mutations as the DNA is passed to the next generation.
Another Example: The history of the gray treefrog, Hyla versicolor, is an example of mutation and its potential effects. When an ancestral Hyla chrysocelis gray treefrog failed to sort its 24 chromosomes during meiosis, the result was H. versicolor. This treefrog is identical in size, shape, and color to H. chrysocelis but has 48 chromosomes and a mating call that is different from the original H. chrysocelis.
These above examples show that mutation can occur in nature rarely. And, if occurred in an organism it changes the genetic sequence a bit.
And, if mutations had occurred again and again during the millions of years of history in the same organism, it can change the genetic sequence a lot and so can create new life forms that is new species.
Mutated DNA are altered DNA that will create a new type of mRNA and so new type of proteins showing different genetic traits, than the original life form. Thus, forming new species.
When a mutated DNA sequence is formed, that mutated DNA can self-replicate and produce more copies. These copies will form RNA and so RNA will later form Proteins. That’s in accordance with the Central Dogma Model.
Thus mutation is also helpful in understanding the Central Dogma’s evidence for evolution.