In basic molecular biology, what chemical components form the two vertical sides of the DNA ladder in the DNA double helix structure?

Introduction / Context:
The classic picture of the DNA molecule is a twisted ladder, called a double helix, which is a central concept in basic molecular biology and genetics. To understand how DNA stores and protects genetic information, it is important to know what the different parts of this ladder are made of. The rungs are formed by nitrogenous bases, while the vertical sides are made from a different set of repeating chemical units. Examinations often test whether learners can correctly identify the components of this structural backbone and distinguish them from other biological substances such as nitrates or simple sugars alone.

Given Data / Assumptions:
- The question refers to the DNA double helix structure, often described as a twisted ladder.
- The focus is on the two vertical sides of the DNA ladder, not the rungs that connect them.
- Options mention combinations like sugars, phosphates, nitrates, and hydrates.
- Standard high school and introductory college biology descriptions of DNA apply.

Concept / Approach:
In the DNA double helix, each strand is a long chain of nucleotides. Each nucleotide contains three main parts: a phosphate group, a five carbon sugar called deoxyribose, and a nitrogenous base. The sugar and phosphate components join together to form a repeating sugar phosphate backbone. This backbone runs along the outside of the DNA molecule and makes up the two vertical sides of the ladder. The nitrogenous bases extend inward and pair to form the rungs. Therefore, to answer the question, we recall that the sides are not made of nitrates or hydrates, but of sugars and phosphates joined in a regular pattern.

Step-by-Step Solution:
1. Recall the basic structure of DNA: a double helix resembling a twisted ladder. 2. Identify the parts of a nucleotide: a phosphate group, a deoxyribose sugar, and a nitrogenous base. 3. Understand that the nitrogenous bases form the rungs of the ladder by specific base pairing. 4. Recognise that the sugar and phosphate groups link together in an alternating chain to form the backbone. 5. Conclude that each side of the DNA ladder is an alternating sequence of sugars and phosphates, known as the sugar phosphate backbone.

Verification / Alternative check:
You can verify this concept by checking any standard biology textbook diagram. The outside of the DNA double helix is always labelled as the sugar phosphate backbone. In such diagrams, deoxyribose sugars are drawn as pentagon shapes and phosphates as circles or small spheres, connected in alternating order along each strand. There is no mention of nitrates or vague hydrates forming the backbone, which confirms that the correct combination is sugars and phosphates. This agrees with the standard molecular model used in school and college level biology courses, and with the classic Watson and Crick depiction of DNA structure.

Why Other Options Are Wrong:
Nitrates and sugars: Nitrates are nitrogen containing ions that are not structural components of the DNA backbone, so this pair is incorrect.
Sugars and hydrates: Hydrates is not a precise term for a structural group in DNA, and DNA sides are not described as containing sugars and hydrates.
Phosphates and nitrates: Although phosphates are correct, nitrates are not part of the DNA backbone, so this pair is wrong.

Common Pitfalls:
A common mistake is to confuse nitrogenous bases with nitrates, because both names contain nitrogen. However, nitrogenous bases are specific organic molecules like adenine and thymine, while nitrates are simple inorganic ions. Another pitfall is to think only of sugar or only of phosphate, rather than the alternating sugar phosphate pattern that actually forms the backbone. Learners may also overfocus on the rungs, but the question clearly asks about the sides of the DNA ladder. Carefully reading which part of the molecule is being described helps avoid these errors.

Final Answer:
The two vertical sides of the DNA ladder are made of sugars and phosphates, forming the sugar phosphate backbone of the double helix.