Most Mammals Have 1000 or More Genes That Encode Receptor

question 34

Multiple Choice

Most mammals have 1000 or more genes that encode receptor proteins on the surface of odor-receptor neurons, so why do some mammals have a better sense of smell than others?

• A) Some of the genes actively transcribing receptor proteins in some species are completely absent in other species.
• B) Some of the genes that code for receptor proteins may have been mutated and rendered inactive in some species but not in others.
• C) Some species, particularly humans, rely much less on odor detection for survival; thus, the genes have mutated to encode proteins that aid in other senses, such as sight.
• D) Some species of mammals have a larger set of "basic odors" than other species.

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