The sides of a ladder are typically made of two long, parallel pieces of material like wood or metal. These sides are connected by rungs or steps that are perpendicular to the sides.

DNA, the molecule often compared to a ladder, has a different structure:

* Sides: The sides of the DNA "ladder" are made of sugar-phosphate backbones.

* Rungs: The rungs are made of pairs of nitrogenous bases (adenine with thymine, guanine with cytosine) that are held together by hydrogen bonds.

So, while the concept of alternating "blanks" and "molecules" is somewhat similar to the structure of DNA, it's not a perfect analogy.