Deoxyribonucleic acid – DNA building block of life

Deoxyribonucleic acid (DNA) is a molecule that contains the biological and genetic information that make each species and each individual unique. In eukaryotes, DNA is found inside a specialised area of the cell called nucleus. Due to the small size of the cell, DNA must be tightly packaged. This packaged form of the DNA is called a chromosome.


DNA is made of chemical building blocks called nucleotides. These building blocks are composed of three essential components: a phosphate group, a sugar moiety, and a nitrogen base. To form a strand of DNA, nucleotides are linked into chains, with phosphate and sugar groups in alternating fashion.

The four types of nitrogen bases found in nucleotides are adenine, thymine, guanine, and cytosine. The composition of bases in a sequence dependent manner determines the function of proteins and its biological instructions.

Basic functions

DNA contains the instructions needed for an organism to develop, survive, and reproduce. To carry out these functions, DNA sequences must be converted into messages that can produce proteins, which are the complex molecules performing most of our body functions. DNA instructions are used to make proteins in a stepwise manner. First specific enzymes read the information in a DNA molecule and transcribe it into intermediates called messenger RNA (mRNA). Next, the information contained in mRNA is translated into amino acids, which are the building blocks of proteins.

During DNA replication, DNA unwinds so that it can be copied. At other times during the cell cycle, DNA also unwinds so that its information can be used to make functional proteins essential for several biological processes. In sexual reproduction, organisms inherit half of their nucleic DNA from the male parent and the other half from the female parent.


National Human Genome Research Institute, NIH, DNA fact sheet, 24th August 2020.