Perception of smells relies on thousands of olfactory receptor genes. It was generally thought that odour representations in the olfactory system is redundant and represented in combinatorial fashion. Individual olfactory receptor gene was, therefore, generally thought to make only a small contribution to behavioural responses provoked by smell.

But the latest findings suggest that single odorant receptor genes can have important, non-redundant functions. Deletion of even a single gene can change behaviour, even behaviour that is important for survival.

The study

Many species depend on their sense of smell for survival. The smell of predator cat urine is innately aversive to mice. This helps a mice to avoid predator cat.

It is the Phenylethylamine found in the urine of cats, which belongs to a class of chemicals called amines, that provokes aversive behaviour in mice.  In mammals, odours are detected by a large number of odorant receptors and a smaller number of trace amine-associated receptors (TAARs). A specific set of these receptors TAARs are necessary for a mice to respond to phenylethylamine and other aversive amines.

Researchers in this study demonstrated that deletion of the Taar gene family, or even a single Taar gene, completely abolishes the mice's aversive behaviour to avoid cats.

Results show that TAARs play non-redundant, specific and important role in the highly sensitive detection of aversive odours, and that the elimination of even a single gene can change vitally important behaviour.