Cytosine (C), thymine (T), adenine (A), guanine (G) these are the nucleotides found in DNA.
C=G and A=T the specific name for the base pair ruling is call chargaffs rules --The first rule states that in DNA the number of guanine units equals the number of cytosine units, and the number of adenine units equals the number of thymine units. This hinted at the base pair makeup of DNA.
The second rule was that the relative amounts of guanine, cytosine, adenine and thymine bases varies from one species to another
also C and G create a 3 hydrogen bond and A and T create a 2 hydrogen bond. these hydrogen bonds allow the double helix to form.
