What is DNA?
A DNA molecule is a complex chemical structure made up of a series of smaller molecules called nucleotides. These are nitrogenous bases that attach to each other through phosphodiester bonds. Nucleotides form base pairs with other nitrogenous bases, forming a polynucleotide. The sequence of the base pairs determines the genetic information of an organism. Each genome is unique to an individual. This sequence is also used to control the functioning of the cell.
When a cell divides, the complementary bases on each strand of DNA pair up to produce a new strand of DNA. This process is called replication. It is essential to the growth of an organism. During this time, the genetic information encoded in the DNA is duplicated and is passed on to the next generation.
The nucleotides in the DNA are composed of a carbon-based sugar molecule and a nitrogenous base. These two molecules form a backbone for the DNA. There are four types of nitrogenous bases. They are adenine (A), cytosine (C), guanine (G), and thymine (T).
All nitrogenous bases form a ring shape, referred to by the prime symbol, "'", which is then numbered clockwise from oxygen. The adenine and thymine strands always pair with the guanine and cytosine strands.
To make a strand of DNA, the phosphate group of one nucleotide attaches to the 5' carbon atom of the next nucleotide. The phosphate and the sugar of the next nucleotide form covalent bonds. Eventually, the entire chain of nucleotide monomers forms the double helix.