DNA is a nucleic acid involved in heredity, or the passing down of genetic traits from one generation to the next. DNA consists of four different types of nucleotide monomers. Which part of the nucleotides' structure is responsible for the incredible variation that exists amongst all types of organisms

Nitrogenous base DNA consists of four unique nucleotides that each contain one unique nitrogenous base—adenine (A), thymine (T), cytosine (C), or guanine (G).

The specific arrangement of these four bases within the DNA of each organism gives that organism its unique traits; here are the arrangements:

-Adenine is paired with Thymine (think of A for apple and T for tree)

-Cytosine is paired with Guanine (think of C for car and G for garage)

search "DNA base pairs" and go to images for better understanding