Certified in Public Health (CPH) Practice Exam

What type of molecules extend from the backbone into the helix of a DNA double helix?

1. Bases

2. Amino acids

3. Lipids

4. Carbohydrates

The correct answer is: Bases

The correct answer is that bases extend from the backbone into the helix of a DNA double helix. In the structure of DNA, the backbone is made up of alternating sugar and phosphate molecules, creating a sturdy framework. Attached to this backbone are the nitrogenous bases—adenine, thymine, cytosine, and guanine—which extend inward towards the center of the helix. These bases pair specifically with one another, adenine with thymine and cytosine with guanine, forming the rungs of the DNA ladder. This base-pairing is crucial for the stability of the DNA structure and for the transmission of genetic information. The way these bases are arranged and paired allows the double helix to maintain its shape and facilitates processes such as replication and transcription, which are fundamental to understanding molecular biology and genetics. In contrast, amino acids are the building blocks of proteins and do not form the structure of DNA. Lipids are primarily associated with cell membranes and energy storage, while carbohydrates serve as energy sources and structural components, none of which are involved in forming the DNA structure or its double helix configuration.