Define gene expression.

• A. The process by which information from a gene is used to synthesize a functional gene product, usually a protein.
• B. The packaging of DNA into chromatin.
• C. The replication of DNA.
• D. The transcription of RNA from a DNA template.

Answer: (A)

Gene expression is the process by which the information encoded by a gene is used to produce a functional product that affects cell function. In practice, this means the gene’s sequence is transcribed into RNA and typically translated into a protein that carries out a cellular function. The definition that the information from a gene is used to synthesize a functional gene product, usually a protein, best captures this outcome. The other options describe related, but distinct, processes: organizing DNA into chromatin, copying DNA for cell division, or transcription alone without forming the final functional product.