Deoxyribonucleic Acid (DNA)

Deoxyribonucleic acid (DNA) is the genetic material of most living organisms. One of its main functions is to produce ribonucleic acid (RNA), which then makes proteins. Thus, information within DNA allows a cell to make most of the molecules it needs to function.

DNA and RNA are nucleic acids that are composed of sugars, phosphates, and nitrogenous bases (or a base). The four bases found in DNA are guanine (G), cytosine (C), thymidine (T), and adenine (A). Each sugar attached to a base and phosphate is called a nucleotide. Hence, DNA is a collection of nucleotides.

Bases from two different strands interact to form a double-helical structure. Guanine forms three hydrogen bonds with cytosine, whereas adenine forms two hydrogen bonds with thymidine. Stacking interactions between the planar bases also stabilize the DNA structure. Phosphates and sugars form the backbone of DNA.

The DNA sequence is represented by writing the base sequence from the 5′ end to the 3′ end of one strand, for example, 5′-GATTACA-3′ represents:

5′-GATTACA-3′

3′-CTAATGT-5′

The sugars and phosphates are omitted in this notation. A comparison of DNA sequences comparison allows one to determine the relationship between different organisms and is also used to find small differences in humans (so-called DNA fingerprinting).

Bibliography

Berg, Jeremy M.; Tymoczko, John L.; and Stryer, Lubert (2002). Biochemistry, 5th edition. New York: W.H. Freeman. Also available from <http://bcs.whfreeman.com/biochem5/>.

Internet Resources

"Basics of DNA Fingerprinting." Available from <http:/www.biology.washington.edu/fingerprint/dnaintro.html>.

"DNA from the Beginning." Available from <http://www.dnaft.org/dnaftb/>.