1. Deoxyribose sugar: This is a five-carbon sugar that forms the backbone of the DNA molecule.

2. Phosphate group: This is a negatively charged molecule that attaches to the deoxyribose sugar and links together the nucleotide units of DNA.

3. Nitrogenous base: This is a molecule that contains nitrogen and can be one of four types: adenine (A), guanine (G), cytosine (C), or thymine (T). These bases pair up with each other (A with T, and G with C) to form the "rungs" of the DNA ladder.

These three parts together form a nucleotide, and many nucleotides linked together form a long DNA strand.