A small segment of DNA that contains the instructions for building a particular protein.

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

Answer: (A)

A gene is a DNA segment that contains the instructions to produce a specific protein. It encompasses the coding sequence that is transcribed into messenger RNA and then translated into a polypeptide, along with regulatory regions that control when and where it is expressed. This makes it the smallest functional unit that fits the description of “a small segment of DNA that contains the instructions for building a particular protein.”

A codon is just a three-nucleotide unit within the mRNA that specifies a single amino acid; it’s part of the gene’s message, not the entire instruction. A chromosome is a large DNA structure made up of many genes, and a genome is the complete set of genetic material.