Which statement correctly summarizes the odor receptor data?

• A. The receptor gene family has about 1,000 genes, with about 350 active, representing about 1% of all genes.
• B. The receptor gene family has about 10,000 genes, with all active.
• C. The receptor gene family has about 350 genes, with about 1,000 active.
• D. The receptor gene family has about 1,000 genes, with all inactive.

Answer: (A)

Odorant receptor genes form a large gene family where only a subset are functional. In humans, there are roughly 1,000 odor receptor genes, but only about 350 of them are active as receptors. Given humans have around 20,000–25,000 genes total, 350 active odorant receptors represent a small fraction—about 1% of all genes. The statement that reflects this pattern is the one describing about 1,000 genes with about 350 active. The other options misstate the numbers or the balance between total and active genes—for example, claiming many more genes, or that all are active, or that most are inactive, would not align with the known data.