June 23, 2005— A little extra DNA makes for faithful males, at least when they are male prairie voles, new genetic research found.
In a study published in the current issue of Science, Larry Young and Elizabeth Hammock of Emory University in Atlanta, Ga., show that fidelity in male voles depends on the length of a particular genetic sequence in a stretch of DNA between their genes.
Voles, mouselike rodents, look pretty much the same, yet they feature dramatic species differences in social behaviors.
Prairie voles (Microtus ochrogaster) form lifelong attachments with a mate, are biparental and highly social, whereas the closely related montane voles (M. montanus) are solitary and promiscuous.
Hammock and Young focused their study on "microsatellites," repetitive DNA sequences that have been long considered junk DNA as they do not produce proteins.
"Most people have considered these microsatellites as not having any function in the genome ... On the contrary, these highly repetitive, unstable DNA sequences are a mechanism generating diversity in behavior … I really think that they have a very important evolutionary function," Young told Discovery News.
The researchers bred two groups of male prairie voles with short and long versions of microsatellite DNA. The scientists put the voles in three situations. They added soiled bedding from unknown females to their cages; put young males into their cages; and allowed males to mate with females for 18 hours.
Then they carried a partner-preference test by adding new females.
It emerged that long sequences activated vasopressin — a hormone produced by mammals that regulates social behavior — in the brain. Voles with the longer strand of DNA spent more time investigating and approached strangers more quickly.
They also were more likely to form bonds with mates, and they spent more time nurturing their offspring.
The longer the microsatellite, the more attentive males were to their female partner and their offspring.
"This is an extraordinary example of research linking gene variation to brain receptors to behavior," said Thomas Insel, director of the U.S. National Institute of Mental Health.
Since people have the same DNA variability as voles, the research might help explain human behavior and behavioral disorders as well.
Said Young: "I'm afraid a DNA test would not be a very accurate predictor for identifying cheating partners. That said, there is a very real possibility that variations in the gene do contribute to these types of behavior. This is something that we are trying to study now."
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the 'junk-dna' is my favourite, too
