There are not four chemicals that hold together the DNA molecule, but rather four nitrogenous bases that pair up to form the rungs of the DNA ladder. These bases are:

* Adenine (A)

* Thymine (T)

* Guanine (G)

* Cytosine (C)

Adenine always pairs with Thymine (A-T) and Guanine always pairs with Cytosine (G-C) through hydrogen bonds, which are weak bonds that are crucial for holding the two strands of DNA together.

While the nitrogenous bases are the primary components of the rungs, the sugar-phosphate backbone provides the structural framework of the DNA molecule. This backbone is composed of alternating sugar (deoxyribose) and phosphate groups.