Central Dogma of Molecular Biology
Central Dogma of Molecular Biology is basically an explanation of how genetic information flows within a biological system. The concept was first brought into the limelight by Francis Crick in 1956. In 1970, it was again stated in a Nature paper. The Central Dogma of Molecular Biology states that sequential information is not transferrable back from protein to either nucleic acid or protein. This precisely means that once information has got into protein, it can never flow back to nucleic acid.
The central dogma of molecular biology is a framework that can help in understanding the way in which sequence information is transferred in living organisms. The sequential information carries biopolymers that include DNA, RNA and protein. The dogma lists three groups of transfers that include general, special and unknown transfers. General transfers are those that take place normally in a variety of body cells. Special transfers on the other hand, are known to occur but limited to certain conditions in the laboratory or in case of viruses. Unknown transfers never take place.
The general transfers that are highlighted above indicate the normal flow of biological information across the body of organisms. According to the central dogma of molecular biology, DNA can be copied to DNA through a process known as DNA replication. Information contained in the DNA can be copied into MRNA through the process of transcription. Proteins on the other hand, can be synthesized through the use of the information that is contained in MRNA. This process is known as translation.
The biopolymers that include RNA, DNA and peptides are classified under linear polymers. This is to say that every monomer is connected to not more than two other monomers. Information is effectively encoded by the sequence of their monomers. According to the transfer of information that is described by the central dogma of molecular biology, one sequence of a biopolymer acts as template for the building of another biopolymer. The newly created biopolymer takes a sequence that is similar to that of the original one.
Despite the central dogma of molecular biology being a concept that most people have agreed with, it should be noted that it has its setbacks too. Some people have questioned certain issues related to the hypothesis and it would be in order that you also get to find out about such concerns. One of the issues is that the hypothesis does not provide information on what the machinery of transfer is made of. Besides, it does not on the aspect of errors.
The central dogma of molecular biology also does not say anything regarding control mechanisms. There is no information about the rate at which the process takes place. According to recent analyses on the central dogma of molecular biology, there are concerns that the hypothesis is not entirely accurate considering that it mainly focuses on proteins as the mediating unit in biological function. Current research is focused on investigating the work of RNA that neither codes nor follows the dogma framework.
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Central dogma of molecular biology
The central dogma of molecular biology refers to the transfer of information from gene sequence to a protein product. It offers a detailed explanation of how DNA codes for RNA, which in turn code for proteins in the body. DNA is the molecule in living things, which carry genetic material and always passes it from parents to offspring. Importantly, it has instructions necessary for the construction of RNA and proteins, which form a whole structure of the body and perform a range of functions. At any moment, molecular machines are always decoding information in DNA and using it to develop proteins. The three types of RNA, which allow this process to go on, are messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).
Transcription in Central dogma of molecular biology
Transcription is the conversion of DNA sequence information into RNA. During this first step of gene expression, a portion of DNA is copied into RNA polymerase. One can compare this to the analogy of copying notes from a textbook. In this, it is so easy to carry notes from the library to wherever you want. Since the library is strictly for research and reading, you would not want to develop your dresser inside the library. Similarly, it would be opposable to carry permanent books from the library to your living room.
It is further important to note that ‘transcribe’ comes from ‘script’, which has a lot to do with writing down sequentially. This forms the basis of understanding the central dogma of molecular biology.
During the initial stages of transcription, the DNA molecular is unzipped partially to allow RNA polymerase to copy the nucleotides of the gene one at a time into an RNA molecule. The structure of RNA has a specific series of nucleotides, just like in DNA. On the other hand, RNA has a single strand, is more fragile and exists as a temporary molecule in the cell as compared to DNA. Moreover, because of its miniature size, RNA can leave the nucleolus freely and get into the cytoplasm, where the manufacture of proteins takes place.
Translation: RNA – Protein
Translation occurs during the central dogma of molecular biology. In this process, the sequence of information encoded within the RNA molecule is decoded and changed into an amino acid sequence. Using the library analogy, translation is equivalent to using library notes to build a dresser from wood by following the notes you obtained from the library. Translation, from its literal meaning, denotes change from one language to another. In this analogy, the translation is from written words in form of notes into a tangible object. In the cell biology, the translation is from nucleotide sequence to amino acid sequence.
While in the cytoplasm, ribosome acts on RNA sequence information, converting it into amino acid sequence. The RNA has three groups of nucleic acids known as codons. Their work is to command the ribosome to supply the chain with a specific amino acid. For instance, the RNNA sequence AAG codes for lysine while sequence GCG codes sequence information for alanine. Normally, cells use twenty amino acids within their protein. It is worth noting that codons are sometimes redundant. This explains why the mathematics of these elements fails to add up.
How reverse translation in Central dogma of molecular biology occurs
Translation and transcription are important processes in central dogma of molecular biology. However, other processes take place, which are essential to the body. One of these processes is reverse transcription. This denotes the opposite of transcription, which we discussed in an earlier section of this article. Reverse transcription thus, is the conversion of information from RNA to DNA. This process does not occur everywhere. Research shows that it happens in retroviruses such as HIV and in eukaryote in retrotransposons. Telomere synthesis also undergoes this process. During reverse transcription, hereditary information from RNA is transcribed or decoded into DNA molecule.
Besides reverse transcription, RNA replication may also take place. This is the duplication of RNA molecule. In other words, RNA molecule is copied to another. RNA-dependent RNA polymerase is an enzyme responsible for this duplication process. It also occurs in several eukaryotes where they are responsible for RNA silencing.
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