The Various Types of RNA


There are different types of RNA in the cell: messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA). More recently, some small RNAs have been found to be involved in the regulation of gene expression.
RNA can be defined as the molecule made up of a single chain of ribonucleotides, each one made up of ribose, a phosphate and one of the four nitrogenous bases (adenine, guanine, cytosine and uracil).
The purines: adenine and guanine, and the pyrimidines cytosine uracil, are complementary.
In DNA, it is a deoxyribose and uracil pyrimidine changes to thymine and is double-stranded.
Cellular RNA is linear and single-stranded, but in the genome of some viruses it is double-stranded.


In cellular organisms it performs several functions. It is the molecule that directs the intermediate stages of protein synthesis, DNA cannot act alone, and uses RNA to transfer this vital information during protein synthesis
Several types of RNA regulate gene expression, while others have catalytic activity. RNA is thus much more versatile than DNA and the latter cannot leave the cell nucleus.
-mRNA is obtained through the transcription of DNA in the nucleus and is used for the synthesis of proteins in ribosomes through the process of transduction.
-RNA (ribosomal) is used to synthesize proteins from mRNA, that is, it is like it helps mRNA to become protein.
-mRNA is the single chain of RNA that is formed from DNA in the transcription process which in eukaryotes takes place in the nucleus of the cell and in prokaryotes it takes place in the cytoplasm.
-Transfer RNA: it is the transfer RNA or tRNA, is a type of ribonucleic acid responsible for transporting amino acids to ribosomes to incorporate them into future proteins during the protein synthesis process.
Each type of tRNA specifically combines with 1 of the 20 amino acids to be incorporated into proteins.
There is more than one tRNA molecule for each amino acid. It leaves the nucleus and carries the message to the cytoplasm, where proteins are assembled by ribosomes.
An anticodon is a group of three nucleotides that pairs with three other nucleotides of the codon of the corresponding messenger RNA (mRNA). The anticodon is located at the end of the «loop» of a transfer RNA (tRNA) molecule.
During the translation process, the anticodons are in charge of pairing with their corresponding codon, so that the tRNA can incorporate an amino acid into the growing polypeptide chain.
-RNAi is a short double-stranded RNA (dsRNA) that prevents specific gene expression by creating disintegration in the chain series of messenger RNA.
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is a conserved biological response to double-stranded RNA that mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
This nucleic acid is usually single-stranded RNA (RNAs) but can be double-stranded RNA (dRNA).
Human diseases caused by RNA viruses include the common cold, influenza, SARS, MERS, COVID-19, dengue virus, hepatitis C, hepatitis E, Nile fever, Ebola disease , rabies, polio and measles.
-siRNA stands for small interfering RNA, small interference RNA (siRNA) or silencing RNA is a class of double-stranded RNA.
It is involved in the mechanism called RNA interference (RNAi), where siRNA interferes with the expression of a specific gene, reducing it.
Furthermore, siRNAs also act in other pathways related to RNAi, such as in antiviral defense or in the organization of the chromatin structure in a genome.
-synthetic dsRNA, usually a small hairpin RNA (shRNA): small hairpin RNA or a short interfering RNA (siRNA).
In both the natural and the experimental routes, an enzyme known as DICER (which is a ribonuclease present in the cytoplasm) is necessary for the formation of miRNA from pre-miRNA or siRNA from shRNA.
-micro-RNA or mi-RNA (microRNA in English) is a single-stranded RNA, between 21 and 25 nucleotides in length, and which has the ability to regulate the expression of other genes through various processes, using the pathway of ribointerference.
Large ds RNA: also by base pairing of complementary RNAs result from transposons and repetitive genes and viruses.
-dsRNAs, symmetric transcription from opposing promoters, these complementary single-stranded RNAs pair up to form double-stranded dsRNAs that are formed when complementary DNA strands are transcribed into RNA.
Viral infection of a cell can produce them, since many viruses form RNAs of both sense and antisense polarity during the replication of their genomes.
The dsRNAs (double strand) can be of endogenous origin (for example the transcripts generated from tandem repeated DNA sequences), or of exogenous origin (such as viruses or transgenes).
-siRNAs silence genes by promoting mRNA cleavage, with exactly complementary sequences, or by recruiting inhibitory proteins.
The name siRNA, comes from the acronym in English small interfering RNA, or silencing RNA is a class of double-stranded RNA.
It is a type of interfering RNA with a length of 20 to 25 nucleotides that is highly specific for the nucleotide sequence of its target messenger RNA.
They originate from a long double strand RNA (dsRNA). The cytoplasmic enzyme that allows this process of transforming dsRNA into siRNA molecules is Dicer.
-miRNA: self-produced single-stranded RNA, short (19-25 nucleotides), encoded by specific genes in multicellular organisms.
They are processed from long single-stranded RNAs that fold into a hairpin structure. They function in the repression of mRNA translation or in the degradation of mRNA.
-HcRNA: an RNA with a closed hairpin turn that can be used to silence the expression of the target gene through RNA interference.
Due to the ability of shRNA to provide specific and long-lasting gene silencing, there has been great interest in the use of shRNA for gene therapy applications, especially in tumors.
ShRNA does not occur naturally like miRNA.


RNAi is the name of the process (RNA interference). RNA interference is a molecular process in which an antisense RNA binds to a complementary target mRNA and drives mRNA cleavage and degradation.
This causes a silencing of gene expression at a non-transcriptional but translational level. It is the name of the effect, not the name of the effector.
miRNA is an endogenous alternative gene silencing process, there are many known miRNAs expressed in certain situations by cells for fine regulation of genes.
Micro-RNAs in animal cells repress gene expression in four different ways:
protein degradation during translation
inhibition of translation elongation
premature termination of translation (disintegration of ribosomes)
inhibition of translation initiation
In recent studies it has been detected that under certain conditions, micro-RNAs can also activate protein synthesis.
Micro-RNAs can function as tumor suppressors or as oncogenes.
Role in viral infection and immune response.
A point polymorphism, also called a single nucleotide or SNP (Single Nucleotide Polymorphism, pronounced snip), is a variation in the DNA sequence that affects a single base (adenine (A), thymine (T), cytosine (C) or guanine (G)) from a genome sequence.
One of these places is found in about one in every 1,000 letters of the code. In this one, one person may have a C and another may have a T.
However, it is generally considered that changes of a few nucleotides, as well as small insertions and deletions (indels) can be considered as SNPs.
Most SNPs do not have much meaning, because they are in a part of the genome that does not have a critical function.
However, some of them confer a risk for a disease such as diabetes or heart disease.
MicroRNAs are small RNA molecules that intervene in different cellular processes through the regulation of gene expression.
They bind by complementarity to certain positions of their target messenger RNAs and facilitate their degradation.
MicroRNAs show high persistence in cells. For example, compared to messenger RNAs that usually degrade in a matter of hours, most microRNAs remain for more than a day and can reach a week in some cases.
This greater stability is due to the fact that the microRNAs are protected from the hostile environment of the cell thanks to their binding to the Argonauta protein, together with which they exert their regulatory function.
Micro-RNAs are RNA molecules transcribed from DNA genes, but they are not translated into proteins.


-Science.2007 Dec 21;318(5858):1931-4. doi: 10.1126/science.1149460. Epub 2007 Nov 29.
Switching from repression to activation: microRNAs can up-regulate translation.Shobha Vasudevan 1, Yingchun Tong, Joan A Steitz.
-Gregory RI, Chendrimada TP, Cooch N, Shiekhattar R. (2005). Human RISC couples microRNA biogenesis and posttranscriptional gene silencing. Cell 123(4):631-40.
types of RNA, messenger RNA, ribosomal RNA, transfer RNA, micro RNA, argonaut protein, which are snips, interference RNA, siRNA or small interfering RNA, long single-strand RNA, shRNA or hcRNA applications, dsRNA or double strand RNA, siRNA small interfering RNA, RNA virus, RNA interference or RNAi, anticodons.

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