ZingPath: Molecular Genetics

DNA stands for deoxyribonucleic acid. It is a nucleic acid and the genetic material of living organisms which stores and transmits the genetic information in cells. There are four nucleotides in DNA, frequently called bases. Because of their specific shape and size, nucleotides adenine and thymine always pair together, and nucleotides cytosine and guanine always pair together in a double helix structure. These nucleotide pairs are held together by chemical bonds, called hydrogen bonds, on the DNA. To picture the structure of DNA, imagine a twisted roller coaster track. The pairs of bases, or nucleic acids, are like the cross ties.

Hereditary characteristics are carried on certain parts of the DNA called genes. Each gene controls a hereditary characteristic, and it carries biological information. The genes are located in a region of the DNA that makes up the chromosomes in the nucleus of a cell. Genes can be as short as 1000 base pairs or as long as several hundred thousand base pairs. This variety in gene pairs allows for great diversity among organisms.

DNA is sometimes compared to a blueprint or a recipe for living organisms. It is what dictates human eye color, hair color, and the shape of ears, among other physical characteristics. Human DNA can be found anywhere there are cells that have nuclei including skin, hair follicles, blood, and saliva. DNA testing and profiling is now used to determine family connections. Since it is, in essence, a genetic fingerprint, DNA evidence also can be used to determine if a person was at a crime scene.

The human body contains 10-100 trillion cells, and each human cell contains about 2.5 meters of DNA. If stretched end to end, DNA from a human body would go to the Sun and back to Earth almost seventy times. Another way to think about is this: DNA from a human body would stretch out past the end of our Solar System over four light days.