Nucleotide: A nucleotide is the basic unit or building block of DNA. It consists of three components: a sugar molecule (deoxyribose), a phosphate group, and one of four nitrogenous bases (adenine, thymine, cytosine, or guanine).
Base pairing: Base pairing refers to the specific interaction between complementary nitrogenous bases in DNA. Adenine always pairs with thymine (A-T), while guanine always pairs with cytosine (G-C).
Hydrogen bonds: Hydrogen bonds are relatively weak chemical bonds between hydrogen atoms and electronegative atoms (like oxygen or nitrogen).