During the 1900s, the following genetic discoveries were made:
DNA is the molecule responsible for inheritance.

There are four bases in DNA, and they combine in a specific way. Adenine pairs with thymine, and guanine pairs with cytosine.

DNA is a double helix. The sugar molecules form the backbone, and the bases are connected by hydrogen bonds in the middle.

Enzymes that can cut and copy sections of DNA are identified and isolated.