Messenger RNA

Messenger RNA (mRNA) is a type of ribonucleic acid that plays a crucial role in protein synthesis within cells. 

It acts as a messenger, carrying genetic information from DNA to the ribosomes, which are the protein-building organelles in cells.

mRNA is transcribed from DNA during transcription. 

In the nucleus of a cell, an enzyme called RNA polymerase binds to a specific region of DNA and starts creating a complementary strand of mRNA. 

This newly synthesized mRNA molecule then carries the genetic code, or instructions, from the DNA to the ribosomes in the cell’s cytoplasm.

Once the mRNA reaches the ribosomes, translation takes place. 

During translation, the ribosomes read the sequence of nucleotides in the mRNA and use that information to synthesize a specific protein. 

The order of the nucleotides in the mRNA determines the order of amino acids, which are the building blocks of proteins.

mRNA is important because it serves as an intermediate between the genetic information stored in DNA and the production of proteins. 

Without mRNA, the genetic code would not be able to be translated into functional proteins necessary for cell structure, function, and various biological processes.

Messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein.

RNA is transcribed in the nucleus; after processing, it is transported to the cytoplasm and translated by the ribosome. 

mRNA really is a form of nucleic acid, which helps the human genome which is coded in DNA to be read by the cellular machinery. 

mRNA is actually the translated form of DNA that the machinery can recognize and use to assemble amino acids into proteins. 

At its end the mRNA is degraded.

mRNA is created during the process of transcription.

In transcription an enzyme , RNA polymerase converts the gene into primary transcript mRNA.

This pre-mRNA usually still contains introns, regions that will not go on to code for the final amino acid sequence. 

Introns are removed in the process of RNA splicing, leaving only exons, regions that will encode the protein. 

This exon sequence constitutes mature mRNA. 

Mature mRNA is then read by the ribosome, and, utilizing amino acids carried by transfer RNA (tRNA), the ribosome creates the protein: 

This process is known as translation. 

As in DNA, genetic information in mRNA is contained in the sequence of nucleotides, which are arranged into codons consisting of three ribonucleotides each. 

Each codon codes for a specific amino acid.

The translation of codons into amino acids requires two types of RNA: 

transfer RNA, which recognizes the codon and provides the corresponding amino acid

ribosomal RNA (rRNA), the central component of the ribosome’s protein-manufacturing machinery.

RNA polymerase transcribes a DNA strand to form mRNA.

The mRNA molecule has a brief existence beginning with transcription, and ultimately ends in degradation. 

An mRNA molecule may be processed, edited, and transported prior to translation. 

A molecule of eukaryotic mRNA and the proteins surrounding it are together called a messenger RNP.

Transcription occurs when RNA is copied from DNA. 

During transcription, RNA polymerase makes a copy of a gene from the DNA to mRNA as needed. 

In prokaryotes RNA polymerase associates with DNA-processing enzymes during transcription so that processing can proceed during transcription. 

It causes the new mRNA strand to become double stranded by producing a complementary strand known as the tRNA strand.

The template for mRNA is the complementary strand of tRNA, which is identical in sequence to the anticodon sequence that the DNA binds to. 

The short-lived, unprocessed or partially processed product is termed precursor mRNA, or pre-mRNA; once completely processed, it is termed mature mRNA.

DNA gene is transcribed to pre-mRNA, which is then processed to form a mature mRNA, and then lastly translated by a ribosome to a protein.

The extensive processing of eukaryotic pre-mRNA that leads to the mature mRNA is the RNA splicing.

RNA splicing is a mechanism by which introns, (non-coding regions). are removed and exons (coding regions) are joined.

Polyadenylation is the covalent linkage of a polyadenylyl moiety to a messenger RNA molecule. 

Polyadenylation occurs during and/or immediately after transcription of DNA into RNA. 

After transcription has been terminated, the mRNA chain is cleaved through the action of an endonuclease complex associated with RNA polymerase. 

ome mRNAs are transported to particular subcellular destinations. 

In mature neurons, certain mRNA are transported from the soma to dendrites, to polyribosomes selectively localized beneath synapses, and mRNAs are also transported into growing axons and especially growth cones. 

mRNAs can also transfer between mammalian cells through structures called tunneling nanotubes.

Because prokaryotic mRNA does not need to be processed or transported, translation by the ribosome can begin immediately after the end of transcription. 

Eukaryotic mRNA that has been processed and transported to the cytoplasm (mature mRNA) can then be translated by the ribosome. 

Coding regions are composed of codons, which are decoded and translated into proteins by the ribosome.

Coding regions begin with the start codon and end with a stop codon.

Different mRNAs within the same cell have distinct lifetime stabilities.

Bacterial mRNA much less stable than eukaryotic mRNA.

In mammalian cells, mRNA lifetimes range from several minutes to days.

The greater the stability of an mRNA the more protein may be produced from that mRNA. 

A limited lifetime of mRNA enables a cell to alter protein synthesis rapidly in response to its changing needs. 

There are many mechanisms that lead to the destruction of an mRNA, some of which are described below.

Inside eukaryotic cells, a balance exists between the processes of translation and mRNA decay. 

The balance between translation and decay is reflected in the size and abundance of cytoplasmic structures known as P-bodies.

Small interfering RNAs (siRNAs) are thought to be part of the innate immune system as a defense against double-stranded RNA viruses.

MicroRNAs (miRNAs) are small RNAs that typically are partially complementary to sequences in messenger RNAs.

Binding of a miRNA to a message can repress translation of that message and accelerate mRNA degradation. 

The administration of a nucleoside-modified messenger RNA sequence can cause a cell to make a protein, directly treat a disease or could function as a vaccine, and indirectly the protein could drive an endogenous stem cell to differentiate in a desired way.

The primary challenges of RNA therapy center on delivering the RNA to the appropriate cells.

Naked RNA sequences naturally degrade after preparation, but may trigger the body’s immune system to attack them as an invader; and they are impermeable to the cell membrane.

RNA must then leave the cell’s transport mechanism to take action within the cytoplasm, which houses the necessary ribosomes.

Gene editing therapies like CRISPR may also benefit from using mRNA to induce cells to make the desired Cas protein.

The first mRNA-based vaccines received authorization and were during the COVID-19 pandemic by Pfizer–BioNTech COVID-19 vaccine and Moderna.

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