Proteins play major roles in cells as enzymes, intervening in chemical reactions or as structural components.
Along with DNA and proteins, ribonucleic acid or RNA is one of the most important molecules that are essential for so many life forms.
A central principle of molecular biology states that the flow of genetic information in a cell is from DNA through RNA to proteins.
RNA is basically what is responsible for carrying the flow of genetic information from DNA in different phases of the processes for the synthesis of proteins.
DNA (deoxyribonucleic acid) is considered the blueprint of the cell; It contains all the genetic information essential for the cell to grow and the organism to develop. RNA, in this role, is the cell’s “DNA photocopy.”
Ribonucleic acid or RNA is a nucleotide polymer and is composed of a ribose sugar, a phosphate, and bases as well, such as adenine , guanine, cytosine, and uracil. RNA is the multiple copies of a part of DNA that can encode a certain protein that the cell requires.
RNA increases the amount of a certain protein that can be produced at one time from a given gene and provides an important checkpoint to regulate when and how much protein is obtained.
In both prokaryotic and eukaryotic cells there are several types of RNA, and the most important are mainly divided into three:
Messenger RNA (mRNA)
Messenger RNA is the most heterogeneous of the 3 types of RNA in terms of base sequence and size. It carries the genetic code copied from DNA during transcription in the form of triplets of nucleotides called codons. This type of RNA is created in the process of transcription.
An mRNA molecule carries a portion of the DNA code to other parts of the cell for processing. During the transcription process, a single strand of DNA is decoded by RNA polymerase, and the mRNA is synthesized.
Physically, mRNA is a chain of nucleotides known as ribonucleic acid and it is single-stranded.
ARN ribosomal (ARNr)
Ribosomal RNA is a molecule in cells that is part of the protein-synthesizing organelle known as the ribosome.
The rRNA travels along the mRNA molecule during translation, coupling amino acids to form a polypeptide chain. For protein synthesis, it binds together with tRNA and other molecules.
Transfer RNA (tRNA)
Transfer ribonucleic acid is a type of RNA molecule that helps decode a messenger RNA sequence in a protein. TRNAs function at specific sites on the ribosome during translation, which is a process that synthesizes a protein from an mRNA molecule.
Proteins are made from smaller units called amino acids, which are specified by three-nucleotide mRNA sequences called codons. Each codon represents a particular amino acid, and each codon is recognized by a specific tRNA.
The tRNA molecule has a distinctive folded structure with three hairpin loops that form the shape of a three-leaf clover.
One of these hairpin loops contains a sequence called the anticodon, which can recognize and decode an mRNA codon. Each tRNA has its corresponding amino acid attached to its end.
When a tRNA recognizes and binds to its corresponding codon on the ribosome, the tRNA transfers the appropriate amino acid to the end of the growing amino acid chain.
The tRNAs and the ribosome then continue to decode the mRNA molecule until the entire sequence is translated into a protein.
There are also other smaller types of RNA such as:
Small nuclear RNA
It is involved in the process of splicing or removing introns from the primary pre-mRNA transcript to create the mature form of the mRNA.
It regulates the expression of at least half of the genes and plays an important role in silencing the genes by blocking the mRNA and preventing its translation.
Small interfering RNA
They are involved in the RNA interference pathway and activate the degradation of the corresponding mRNA and prevent it from being translated into proteins.