Scientists seek sources of sexy smells.

Scientists seek sources of sexy smells

Researchers have garnered another clue to the puzzling role of odor in mate selection and pregnancy outcome in mice. Though the finding may not prove sufficiently relevant in humans to justify returning your holiday-gift colognes, it serves as a reminder of some of the subtle mechanisms that can influence reproductive decisions.

Scientists have known for years that a female mouse, given a choice of two mates -- one genetically identical to her and one slightly different -- will usually choose the male featuring some genetic difference. This holds true even if the difference amounts to nothing more than a minor variation in only one out of thousands of genes. Researchers know that this discrimination is odor-induced, and that odors can affect a mouse's physiology even after mating. For example, if a recently mated female is caged near a male featuring a slightly different genetic makeup (and thus a slightly different smell) than that of the male she just mated with, she often will spontaneously abort -- a phenomenon called pregnancy block. Genes capable of inducing pregnancy block seem to be present on several chromosomes.

Kunio Yamazaki of the Monell Chemical Senses Center in Philadelphia and his colleagues now report they can induce pregnancy block in mice exposing the females to two males that differ genetically from each other only in a portion of their Y chromosome. That's surprising, says co-worker Edward A. Boyse of the University of Arizona in Tucson, because the tiny Y chromosome, whose function appeared essentially limited to gender determination in mice, seems not to display the genetic variability thought necessary to code for complex phenomena such as odor types. Their report appears in the December PROCEEDING OF THE NATIONAL ACADEMY OF SCIENCES (Vol.86, No.23).