Here's a breakdown:
* Nitrogenous bases: These are the "letters" of the genetic code and come in four types: adenine (A), guanine (G), cytosine (C), and thymine (T).
* Hydrogen bonds: These are weak bonds that hold the nitrogenous bases together in pairs: A always pairs with T, and C always pairs with G.
* Pairing: These pairs form the "rungs" of the DNA ladder, with the sugar-phosphate backbone forming the sides.
So, the middle of the DNA molecule is essentially a series of these base pairs, connected by hydrogen bonds, which hold the two strands of the DNA double helix together.
