DNA: DNA (deoxyribonucleic acid) is the genomic material in cells that contains the genetic information used in the development and functioning of all known living organisms. DNA, along with RNA and proteins, is one of the three major macromolecules that are essential for life. Most of the DNA is located in the nucleus, although a small amount can be found in mitochondria (mitochondrial DNA). Within the nucleus of eukaryotic cells, DNA is organized into structures called chromosomes. The complete set of chromosomes in a cell makes up its genome; the human genome has approximately 3 billion base pairs of DNA arranged into 46 chromosomes. The information carried by DNA is held in the sequence of pieces of DNA called genes.
RNA: It is another macromolecule essential for all known forms of life. Like DNA, RNA is made up of nucleotides. Once thought to play ancillary roles, RNAs are now understood to be among a cell’s key regulatory players where they catalyze biological reactions, control and modulate gene expression, sensing and communicating responses to cellular signals, etc.
The chemical structure of RNA is very similar to that of DNA: each nucleotide consists of a nucleobase a ribose sugar, and a phosphate group. There are two differences that distinguish DNA from RNA: (a) RNA contains the sugar ribose, while DNA contains the slightly different sugar deoxyribose (a type of ribose that lacks one oxygen atom), and (b) RNA has the nucleobase uracil while DNA contains thymine. Unlike DNA, most RNA molecules are single-stranded and can adopt very complex three-dimensional structures.