The DNA structure is similar to a ladder. Choose the molecules that make up the "rails"
or sides of the DNA structure.
ribose
guanine
adenine
thymine
deoxyribose
phosphate
uracil
cytosine

The molecules that make up the "rails" or sides of the DNA structure are deoxyribose and phosphate

Explanation: A DNA is a double stranded helix made up of nucleotides. A nucleotide is made up of three parts: a deoxyribose sugar, a phosphate group and a nitrogenous base. Nitrogenous bases found in DNA are Adenine, Thymine, Cytosine and Guanine. The bases pairs with each other to form the rungs of the ladder while the phosphate group and deoxyribose sugar forms the rail or the backbone. The rail containing phosphate groups and deoxyribose sugars is called the phosphodeoxyribose backbone.

a tetrad is the foursome during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids.