Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

What component of a DNA molecule carries the information for protein synthesis?

1. Sugars

2. Phosphate groups

3. Nitrogenous bases

4. Amino acids

The correct answer is: Nitrogenous bases

The component of a DNA molecule that carries the information for protein synthesis is the nitrogenous bases. DNA is structured as a double helix, with its backbone made up of sugars and phosphate groups. However, the specific sequences of the nitrogenous bases—adenine, thymine, cytosine, and guanine—encode the genetic information necessary for producing proteins. These bases pair in a complementary manner, with adenine pairing with thymine and cytosine pairing with guanine. The sequence of these bases determines the sequence of amino acids in a protein, which is critical because it ultimately dictates the structure and function of the protein being synthesized. This flow of information from DNA to RNA, and then to protein, is often referred to as the central dogma of molecular biology. While sugars and phosphate groups form the structural framework of the DNA molecule, they do not carry genetic information. Amino acids are the building blocks of proteins and are crucial for protein synthesis, but they are not components of DNA itself. Instead, amino acids are assembled based on the instructions carried by the nitrogenous bases through the intermediary molecule, mRNA (messenger RNA).