Definition of Central Dogma
A Central Dogma describes how DNA is converted to RNA and then into Proteins in Molecular Biology. A genomic process refers to the conversion of DNA information into a functional product.
RNA serves as a messenger to carry information through the Ribosomes as DNA provides instructions for making Proteins.
The Central Dogma is the biological process that transfers Genetic information from DNA to RNA, and then into Proteins.
What is the Central Dogma?
A Central Dogma is an explanation of the flow of Genetic information in a cell, including the replication of the DNA, the transcription of the RNA, and the translation of the RNA to create the Proteins.
It is possible to understand the concept of interaction through the framework. For example, biopolymers are common. Biopolymers are primarily composed of Proteins, RNA, and DNA, which can further be divided into general and unknown transfers.
In the laboratory, special transfers are made in exceptional cases. Cells are generally transferred by general means. Information is constantly flowing through transcription and translation in the human body. It is believed that unknown transfers never occur.
As a result, two new strands of DNA are created, one strand from the parent DNA and one from the newly synthesized DNA. This is called semiconservative DNA replication.
Steps of the Central Dogma
The central dogma takes place in two tages:
1. Transcription
The enzyme RNA Polymerase transfers information from one strand of DNA to another strand of RNA during transcription. Three parts of the DNA strand are involved in this process: the promoter, the structural gene, and the terminator.
DNA strands that synthesize RNA are called template strands, and DNA strands that Code for RNA are called coding strands. RNA polymerases that are DNA-dependent bind to the promoter and catalyze the 3' to 5' directions of polymerization.
The newly synthesized RNA strand is released from the terminator sequence as it approaches the terminator. RNA strands released after transcription undergo further modifications post-transcriptionally.
2. Translation
Proteins are enCoded by RNA by a process called translation. Translation involves energy and is an active process. The energy comes from the charged tRNA Molecules.
The translation process is initiated by ribosomes. Ribosomes are made up of two subunits, one larger and one smaller. As a result, the larger subunit consists of two tRNA Molecules positioned together so that enough energy can be expended to form a peptide bond.
The mRNA enters the smaller subunit and is then held by the tRNA Molecules present in the larger subunit that are complementary to the codon. In this way, two codons are held together by two tRNA Molecules placed close together and a peptide bond is formed between them. This process results in long polypeptide chains of amino acids.
Genetic Code
Proteins are manufactured from RNA and their Genetic Code contains information about them. In general, three nucleotides and four nitrogenous bases collectively Code for an amino acid, forming a triplet codon. As a result, there are 64 amino acids possible, including 4 x 4 x 4 amino acids. There are 20 amino acids found naturally.
As a result, the Genetic Code deteriorates. Due to the characteristics of the Genetic Code, some amino acids are enCoded by more than one codon at a time, causing the amino acid to degenerate. There is only one codon for each amino acid and the Code is universal regardless of the organism.
In total, there are 64 codons, of which three are stop codons that end transcription and one is an initiator codon, i.e. AUG, which Codes for methionine.
FAQs on Central Dogma of Molecular Biology
1. What is the central dogma of molecular biology?
The central dogma of molecular biology, first proposed by Francis Crick, describes the fundamental process of how genetic information flows within a biological system. It states that information is transferred from DNA to RNA and then from RNA to Protein. This unidirectional flow is essential for converting the genetic blueprint encoded in DNA into functional products like proteins that carry out cellular functions.
2. What are the three main processes described by the central dogma?
The central dogma outlines three core processes that manage and express genetic information:
- Replication: The process where a DNA molecule is duplicated to produce two identical DNA molecules. This is crucial for cell division.
- Transcription: The process of creating a messenger RNA (mRNA) copy from a DNA template. This occurs in the nucleus of eukaryotic cells.
- Translation: The process where the genetic code on the mRNA is read by ribosomes to synthesize a specific protein. This occurs in the cytoplasm.
3. Where do transcription and translation occur within a eukaryotic cell?
In eukaryotic cells, the processes of the central dogma are separated by location. Transcription, the synthesis of RNA from a DNA template, occurs inside the nucleus, where the cell's DNA is protected. The resulting mRNA molecule is then transported out of the nucleus to the cytoplasm, where translation takes place on ribosomes.
4. Why is the central dogma considered a two-step process for making proteins (transcription and translation)?
The two-step process is crucial for cellular efficiency and protection. Using an mRNA intermediate serves two main purposes:
- Protection: It keeps the original DNA master copy safe within the nucleus, preventing potential damage during protein synthesis.
- Amplification: A single gene (DNA) can be transcribed into hundreds or thousands of mRNA molecules. Each mRNA can then be translated multiple times, allowing the cell to produce large quantities of a specific protein quickly when needed.
5. How does reverse transcription challenge the original concept of the central dogma?
Reverse transcription is a key exception to the unidirectional flow of information described by the central dogma. In this process, the enzyme reverse transcriptase uses an RNA molecule as a template to synthesize a complementary DNA (cDNA) strand. This 'RNA → DNA' flow is observed in retroviruses, such as HIV, and demonstrated that genetic information can, under certain circumstances, flow in the reverse direction, adding a layer of complexity to the original dogma.
6. What is the role of the genetic code in the central dogma?
The genetic code is the set of rules that links the sequence of nucleotides in mRNA to the sequence of amino acids in a protein. During translation, the ribosome reads the mRNA in three-nucleotide units called codons. Each codon specifies a particular amino acid (e.g., AUG codes for Methionine) or signals the process to stop. This code is the 'language' that makes the final step of the central dogma—protein synthesis—possible.
7. How does the central dogma process differ between prokaryotic and eukaryotic cells?
The main difference lies in the location and timing of the processes. In eukaryotic cells, transcription happens in the nucleus and translation happens in the cytoplasm, so they are separate events. In prokaryotic cells, which lack a nucleus, transcription and translation are coupled. This means that translation can begin on an mRNA molecule even while it is still being transcribed from the DNA.
8. What are some examples of the central dogma's importance in medicine?
Understanding the central dogma is critical for modern medicine. For example:
- Antiviral Therapies: Drugs for retroviruses like HIV often work by inhibiting reverse transcriptase, thereby blocking the virus's ability to integrate its genetic information into the host cell.
- Antibiotics: Many antibiotics target the bacterial ribosome, disrupting the translation process and preventing bacteria from producing essential proteins.
- Genetic Disease Treatment: Gene therapies aim to correct or supplement faulty genes, directly intervening in the central dogma to produce a functional protein.
