What term describes a DNA segment that contains instructions for building a particular protein?

• A. Codon
• B. Genome
• C. Gene
• D. Chromosome

Answer: (C)

The essential idea here is a gene. A gene is a specific stretch of DNA that carries the instructions to synthesize a particular protein (or, in some cases, a functional RNA). The information in that sequence is used in transcription to make an mRNA copy, which is then translated into the protein with the correct order of amino acids. A codon is only a single three-nucleotide unit within the gene that encodes one amino acid, so it’s too small to describe the entire set of instructions. The genome refers to all of an organism’s genetic material, not just one segment, while a chromosome is a larger DNA molecule that contains many genes. Therefore, the DNA segment that contains the instructions for building a specific protein is a gene.