What is the approximate total number of odor receptor genes in the family?

What is the approximate total number of odor receptor genes in the family?

• A. About 1,000
• B. About 350
• C. About 2,000
• D. About 100

Answer: (A)

Odor receptor genes form a very large gene family that expands through duplications over evolutionary time. In humans, the olfactory receptor (OR) gene family includes about 1,000 genes in total, though only roughly 350–400 are still functional. The rest are pseudogenes that no longer code for functional receptors. Because the question asks for the total number of odor receptor genes in the family, about 1,000 is the best estimate. The smaller figure reflects only the functional genes, the larger figures would exceed what’s seen in the genome.

Odor receptor genes form a very large gene family that expands through duplications over evolutionary time. In humans, the olfactory receptor (OR) gene family includes about 1,000 genes in total, though only roughly 350–400 are still functional. The rest are pseudogenes that no longer code for functional receptors. Because the question asks for the total number of odor receptor genes in the family, about 1,000 is the best estimate. The smaller figure reflects only the functional genes, the larger figures would exceed what’s seen in the genome.