DNA is a deoxyribonucleic acid. DNA is a nucleic acid
that contains genetic instructions. This is used in the development and
functioning of all known living organisms. The main role of DNA molecules is
the long-term storage of information.
Chemically, DNA is a long polymer of simple units
called nucleotides, with a backbone made of sugars and phosphate groups joined
by diester bonds. Bases are the molecules attached to each other. Bases may be
of A, T, G and C abbreviated as Adenine, Thymine, Guanine and Cytosine
respectively. It is on these bases that DNA encode information. This
information is read through genetic code, which specifies the sequences of
amino acids within proteins.
The monomer units of DNA are nucleotides, and the
polymer is known as polynucleotide. Each nucleotide consists of a 5-carbon
sugar (deoxyribose), a nitrogen containing base attached to the sugar, and a
phosphate group. Adenine and Guanine are purines. Purines are double ringed
structures. Cytosine and Thymine are single ringed structures and are known as
pyramidines. The deoxyribose sugar of the DNA has 5 carbons and 3 oxygens.
Deoxyribose lacks hydroxyl group at the 2’ position when compared to ribose,
the sugar component of RNA.
A nucleoside is one of the four DNA bases covalently
attached to the C1 position of a sugar. The sugar in ribonucleotides is ribose.
Nucleosides differ from nucleotides in that they lack phosphate group.
Nucleotide is a nucleoside with one or more phosphate groups covalently
attached to the 3’ and 5’ hydroxyl groups.
The DNA backbone is a polymer with an alternating
sugar-phosphate sequence. The deoxyribose sugar are joined at 3’ hydroxyl as
well as 5’ hydroxyl groups to the phosphate groups with bonds known as
phosphodiester bonds.
So, DNA consists of mainly sugar groups, phosphate
groups, nucleotides such as Adenine, Guanine, Thymine and Cytosine. It is also
considered as the genetic material in an organism.
Read more about DNA in What is DNA Made of? Part 2