Deoxyribonucleic Acid (DNA)

DNA is the hereditary material found in humans and other organisms. DNA, found in nucleus of a cell is known as nuclear DNA and found in mitochondria is known as mitochondrial DNA (NIH, 2014). Genes and chromosomes are made up of DNA and human body contains 20,000 to 25,000 genes (NIH, 2014). Building block of DNA is nucleotide. Nucleotide consists of a pentose sugar, a phosphate group and a nitrogenous base (IPGRI and Cornell University, 2003). Nitrogen-containing molecules or nitrogen bases guanine and adenine are called purines and cytosine and thymine are called pyrimidine.

DNA has unique double helix structure. DNA model and double helix structure was proposed by James Watson and Francis Crick in 1953. DNA structure has sugar phosphate backbone. Double helix of DNA is formed by base pairs of Adenine-Thymine (AT) and Guanine-Cytosine (GC). Two DNA strands are joined by hydrogen bonds to form double helix structure (Clark, 2013).  Glycosidic is the bond between a nitrogenous base and a sugar phosphate molecule and Phosphodiester is the bond between the sugar phosphates. The hydrogen bond joining the two strands of DNA is weaker than glycosidic or phosphodiester bonds.

Hydrogen bond can be broken to separate two strands of DNA at higher temperature around 100o C with polymerase chain reaction (PCR) and the process is called denaturation or melting (May, n.d.). Renaturation or annealing is the process of connecting two strands of DNA with hydrogen bond (May, n.d.). DNA can be replicated to produce two genetically identical daughter cells (NIH, 2014).


Clark, J. (2013) DNA-Structure [Online] Available at [Accessed on 27 January 2014].

May, P (n.d.) DNA: Deoxyribonucleic Acid [Online] Available at [Accessed on 27 January 2014].

IPGRI and Cornell University (2003) Using Molecular Marker Technology in Studies on Plant Genetic Diversity [Online] Available at [Accessed on 12 January 2014].

National Institute of Health (NIH)(2014) Cells and DNA [Online] Available at [Accessed on 12 January 2014].


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