What is RNA?

What Does RNA Mean

We explain what RNA is, what its structure is like and the different functions it performs. Also, its classification and differences with DNA.

RNA is present inside both prokaryotic and eukaryotic cells.

What is RNA?

RNA (Ribonucleic Acid) is one of the elemental nucleic acids for life , responsible together with DNA (deoxyribonucleic acid) for the work of protein synthesis and genetic inheritance.



This acid is present inside both prokaryotic and eukaryotic cells , and even as the only genetic material of certain types of viruses (RNA viruses), and consists of a molecule in the form of a single chain of nucleotides (ribonucleotides) formed in turn by a sugar (ribose), a phosphate and one of the four nitrogenous bases that make up the genetic code : adenine, guanine, cytosine or uracil.

It is generally a linear and single-stranded (single-stranded) molecule, and fulfills a variety of functions within the complex of the cell , which makes it a versatile executor of the information contained in DNA.

RNA was discovered together with DNA in 1867 , by Friedrich MIescher, who called them nuclein and isolated them from the cell nucleus , although their existence was later proven also in prokaryotic cells , without a nucleus. The mode of RNA synthesis in the cell was later discovered by the Spanish Severo Ochoa Albornoz, winner of the Nobel Prize in Medicine in 1959.

The understanding of how RNA operates and its importance for life and evolution, made possible the emergence of theses on the origin of life, such as the one that intuits in 2016 that the molecules of this nucleic acid were the first forms of life in exist (in the RNA world Hypothesis ).

See also: Bacteria

RNA structure

Nucleotides are made up of a monosaccharide sugar molecule called ribose.

Both DNA and RNA are made up of a chain of units known as monomers , which are repeated and are called nucleotides; These are linked together by negatively charged phosphodiester bonds. Each of these nucleotides is made up of:

  • A monosaccharide sugar molecule called ribose (other than deoxyribose in DNA).
  • A phosphate group (salts or esters of phosphoric acid).
  • A nitrogenous base: Adenine, Guanine, Cytosine or Uracil (in the latter it differs from DNA, which has Thymine instead of Uracil).

These components are organized based on three structural levels, which are:

  • Primary. The linear sequence of nucleotides that define the following structures.
  • High school. Since RNA folds on itself due to intramolecular base pairing, its secondary structure refers to the shape it takes during folding: helix, loop, hairpin loop, bulge, pseudo-knot, etc.
  • Tertiary. Although RNA does not form a double helix like DNA in its structure, it does tend to form a single helix as a tertiary structure, as its atoms interact with the surrounding space.

RNA function

RNA fulfills numerous functions, the most important being protein synthesis , in which it copies the genetic order contained in DNA to use it as a standard in the manufacture of proteins and enzymes and various substances necessary for the cell and the organism. To do this, it goes to the ribosomes, which operate as a kind of molecular protein factory, and it does so by following the pattern printed by DNA.

RNA types

There are several types of RNA, depending on their primary function:

  • Messenger or coding RNA (mRNA). It is responsible for copying and carrying the exact sequence of amino acids from DNA to the ribosomes, where instructions are followed and proteins are synthesized.
  • Transfer RNA (tRNA). These are short polymers of 80 nucleotides that have the mission of transferring the pattern copied by the mRNA to the ribosomal RNA, serving as an assembly machine, choosing the correct amino acids based on the genetic code.
  • Ribosomal RNA (rRNA). Its name comes from the fact that it is found in the ribosomes of the cell, where they are combined with other proteins. They operate as catalytic components to "weld" the newly assembled proteins onto the mRNA template. They act, thus, as ribozymes.
  • Regulatory RNAs. They are complementary pieces of RNA, in specific regions of mRNA or DNA, that can perform various tasks: interference in replication to suppress specific genes (RNAi), activators of transcription (antisense RNA), or regulate expression gene (long cRNA).
  • Catalyst RNA. Pieces of RNA that operate as biocatalysts, operating on the synthesis processes themselves to make them more efficient or to ensure their correct development, or even to put them fully into operation.
  • Mitochondrial RNA. Since the cell's mitochondria have their own protein synthesis system, they also have their own forms of DNA and RNA.


RNA is a smaller and more complex molecule than DNA.

The difference between RNA and DNA is based, first of all, on their constitution: as has been said, RNA has a different nitrogen base (uracil) than thymine and is composed of a different sugar than deoxyribose (ribose).

Apart from this, DNA has a double helix in its structure , that is, RNA is a smaller and more complex molecule, which has a much shorter life span in our cells.

However, their differences are more profound, since DNA serves as a bank of information, an ordered pattern of the elemental sequence that allows us to build the proteins in our body; while the RNA is its reader, transcriber and executor : the one in charge of reading the code, interpreting it and materializing it.

Follows with: DNA

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