Which of the following best defines a gene and its relationship to gene expression? (Choose the most concise, correct definition. Use recall strategy.)

• A. A gene can be described as a heritable unit of DNA sequence that, when transcribed into RNA and then translated into polypeptide chains in the cytoplasm by ribosomes and associated factors, ultimately produces proteins whose abundance is modulated by many cellular processes including promoter accessibility, post-transcriptional RNA processing, translational regulation, and eventual protein degradation pathways.
• B. A gene is a segment of DNA that encodes a product, usually a protein; gene expression is the process of producing that product through transcription and translation.
• C. A gene is a protein that controls traits and gene expression is the amount of protein already present in the diet that influences phenotype.
• D. A gene is an organelle that manufactures ribosomes and gene expression refers to the number of ribosomes inside the nucleus.

Answer: (B)