Approximately how many odor receptor genes are active in humans?

Approximately how many odor receptor genes are active in humans?

• A. About 350
• B. About 1,000
• C. About 650
• D. About 50

Answer: (A)

Humans have a very large odorant receptor gene family, but many copies are nonfunctional. The number of actually active, functional receptors is a few hundred, typically estimated around 350 to 400. The most accurate single figure among these options is about 350 because it reflects the functional repertoire rather than the total gene count. The other numbers overstate the active set: about 1,000 would correspond to total gene loci (including nonfunctional ones), about 650 is still higher than the usual functional count, and about 50 would significantly underestimate how many receptors contribute to detecting odors.

Humans have a very large odorant receptor gene family, but many copies are nonfunctional. The number of actually active, functional receptors is a few hundred, typically estimated around 350 to 400. The most accurate single figure among these options is about 350 because it reflects the functional repertoire rather than the total gene count. The other numbers overstate the active set: about 1,000 would correspond to total gene loci (including nonfunctional ones), about 650 is still higher than the usual functional count, and about 50 would significantly underestimate how many receptors contribute to detecting odors.