What is an RNA?

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Ribonucleic acids (RNA) is a biologically important type of macromolecule that consists of a long chain of nucleotide units. Each nucleotide consists of a nitrogenous base, a ribose sugar, and a phosphate. RNA is very similar to DNA, but differs in a few important structural details:



  1. In the cell, RNA is usually single-stranded, while DNA is usually double-stranded. RNA also has a much shorter chain of nucleotides.


  2. The RNA nucleotides contains ribose while DNA contains deoxyribose, a type of ribose that lacks one oxygen atom and contains no hydroxyl group attached to the pentose ring in the 2' position. These hydroxyl groups make RNA less stable than DNA because it is more prone to hydrolysis. They also slightly change the structure of these chains which results RNA’s ability to form very stable tertiary structures.


  3. RNA has the base uracil which is which is an unmethylated form of thymine, its DNA counterpart.




RNA is transcribed from DNA by enzymes called RNA polymerases and is generally further processed by other enzymes. In protein synthesis, a type of RNA called messenger RNA carries information from DNA to structures called ribosomes. These ribosomes are made from proteins and ribosomal RNAs, which come together to form a molecular machine that can read messenger RNAs and translate the information they carry into proteins. There are many RNAs with other roles – in particular regulating which genes are expressed, and as the genomes of most viruses.