Two of the bases A, T, C, and G, which weakly link to form a “rung of the DNA ladder.” A DNA nucleotide is made of a molecule of sugar, a molecule of phosphoric acid, and a molecule called a base. The bases are the “letters” that spell out the genetic code and are the data bits of the encoded information in the DNA. The code letters are A, T, C, and G, which stand for the chemicals Adenine, Thymine, Cytosine, and Guanine, respectively. When these bases form the base pairs, which are the rungs of the DNA ladder, Adenine always pairs with Thymine (AT or TA), and Cytosine always pairs with Guanine (CG or GC). The base pair is the portion of the DNA molecule in which the basic nucleotide instruction bit or data point of information of the genetic code is embedded. Base pair combinations provide a chemically stable and reliable method of storing the DNA information at the data bit level. These base pairs are the rungs of the ladder in the DNA molecule. The human genome contains about 3.2 billion base pairs (bp) or rungs of the ladder, or in other words 3.2 billion pieces of information. If each nucleotide piece of data in the genome DNA sequence was stored in a text file on a computer’s hard disk using its representative base letter, i.e., A, T, C, or G, it would take at least a 3.2 giga-byte hard drive to hold it all.

This definition is in context to Genetics and Genealogy. See more contextual defintions for Base Pair (Bp).