DNA is the full genetic information that determines the nature and function that an animal has. Proteins are made by the genetic code contained in DNA. Conversion of DNA encoded data to RNA is necessary to make proteins. So, in the majority of cells, genetic information is transferred from – DNA to RNA, and then to protein. The transfer of information is controlled by three different processes that help in the transfer of genetic information as well as its transformation into a different form:
- Replication: A double-stranded nucleic acid is duplicated in order to create identical copies. This process preserves gene information.
- Transcription: A DNA segment which is a gene transscribed and read to form a one-stranded segment of the RNA. The RNA is transferred from the nucleus to the celluloid.
- Translation: The sequence of RNA transforms into amino acids in the process of forming the protein. In the process of translation the ribosome is able to read 3 bases (a codon) at each interval from the sequence of RNA, and transforms them into an amino acid.
The flow of information can be unidirectional, and indefinitely.
This is the most straightforward method of how is the Central Dogma of Molecular Biology is explained.
In the larger scheme, the fundamental doctrine that is molecular biological research provides the explanation of the transmission of genetic information in the biological system. It was first articulated in the work of Francis Crick in 1958, in the form of “Once the ‘information’ is passed into proteins, it is impossible to return to the protein. In further detail, the transfer details from nucleic acids to nucleic acids or from protein to nucleic acid might be possible, but the transfer of information from protein to protein or from nucleic acid to protein is not possible.”
What is the ‘Central Dogma’?
The Central Dogma is the method by which DNA’s instructions transform into a functional product. It was first suggested in the year 1958 by Francis Crick, discoverer of DNA’s structure.
- The principal tenet of molecular biology is the transfer of genetic information through DNA into RNA to create a functional product called which is a protein.
- The main dogma is that DNA has the necessary information to create the proteins we use and that RNA acts as the messenger that delivers these details into the ribosome.
- The ribosomes function as factories within the cell, where information is ‘translated into a functional product.
- The process through which DNA instructions are transformed into a functional product is known as gene expression.
- Expression of genes is achieved through two major steps – transcription as well as translatio.
- In transcription, the information contained in the DNA of all cells is converted into tiny portable messages in RNA.
- In translation, the messages are transferred from the point where the DNA is located in the cell nucleus to ribosomes from where they are read and translated into specific proteins.
- The central dogma says that the structure of information that occurs the most frequently in cells is:
- With existing DNA, you can make the new DNA (DNA replication)
- From DNA to create new transcripts of RNA (transcription)
- From RNA to create the new protein (translation).
- Reverse transcription involves an exchange of information between RNA in order to create new DNA. This is the case with retroviruses, like HIV. It is the process through which genetic information derived from DNA is put together to form new DNA.
The Dogmas
The dogma provides a framework to understand the transfer of information in sequence between biopolymers carrying information DNA and RNA (both Nucleic Acids) and protein. There are 3×3=9 possible transfer of information in direct ways that could occur between these. The dogma classifies them into three groups:
A. Three general transfers
It describes the regular circulation of information in biological systems. DNA can be copied onto DNA (DNA replication) DNA information may be transferred into MRNA (transcription) as well as proteins are made using the information found in the mRNA template (translation). It is believed that it occurs typically in the majority of cells.
B. Three special transfers
The specific transfers explain the process of copying RNA from the RNA (RNA replication) DNA is synthesized by using an template RNA (reverse transcription) and proteins synthesized directly from a DNA-based template without the need for an mRNA. Temin (1970) revealed the presence of the enzyme “RNA dependent DNA polymerase” (inverse transcriptase) that can synthesize DNA using only a single strand of DNA template. Baltimore (1970) as well described the activities the enzyme could have in specific tumor viruses based on RNA.
This groundbreaking discovery in molecular biology led to the idea that the central doctrine reverse” or teminism. This suggests that the order of information flow does not have to be that of DNA and protein, but may also occur from DNA to RNA. It has been observed in certain circumstances in the case of certain viruses or when in a laboratory.
C. Three unknown transfers
The unidentified transfers are the copying of a protein from a protein; synthesis of RNA using the basic structure of the protein as an example DNA synthesis employing the structure of the protein as the template. They aren’t thought to naturally occur.
Central Dogma Steps
The central dogma is formulated in two distinct steps:
Transcription
Transcription is the method by which details are transferred from one part of DNA to RNA via an enzyme called RNA Polymerase. The DNA strand that undergoes the process is comprised of three elements: structural gene, promoter and an endorsor.
The DNA strand that produces the RNA is referred to as the template strand. The second strand is referred to as the code the strand. The DNA-dependent RNA Polymerase binds to the promoter and initiates the polymerization process in the 3′-5 direction.
As it gets closer to its terminator sequence ends with the freshly synthesized the RNA Strand. This newly-released RNA strand undergoes post-transcriptional modification.
Translation
The process of translation is by which RNA codes specific proteins. This is an energetic process that requires energy. The energy is supplied by the charged molecules of tRNA.
Ribosomes are the ones that initiate the process of translation. They are composed of a bigger subunit and smaller subunit. The larger subunit, on the other hand, is composed of two tRNA molecules positioned close enough to allow a it is possible to form a peptide bond with the help of sufficient energy.
The mRNA is transferred to the smaller subunit and is held by TRNA molecules of the complementing codon that is located within the bigger subunit. So, two codons will be held together by two molecules of tRNA that are placed near to one another and a peptide bonds is created between the two codons. In the course of this process long polypeptide chains composed of amino acids get created.
Genetic Code
Genetic code is information about the protein derived from RNA. There are three nucleotides as well as four nitrogenous bases. They make up an encoding codon called a triplet that encodes an amino acid. So, the total amount of amino acids that can be produced could be 4 x 4 four which is 64 amino acids. There are 20 naturally occurring amino acids.
The genetic code is degenerate. This is explained by particulars in the genetic code that is, a small number of amino acids are encoded by more than one codon , leading to them degenerating. Each codon codes only one amino acid, which is why the codon codes can be universal, regardless of the kind of organism.
Of the 64 codons there are 3 that are stop codons, which end transcription. Another Codon is an initiate codon i.e. AUG is the code for Methionine.
Significance of the Central Dogma of Molecular Biology
This is why the central dogma is the fundamental structure for how genetic information moves through a DNA sequence an underlying protein product within cells, and provides an understanding of the crucial functions that take place inside cells.
