Researchers take first look at the genetic dynamics of inbreeding ...( Researchers have taken a first look ...)

Researchers have taken a first look at the broad genetic changes that accompany reproductive declines in inbred populations.

Although scientists have known for more than a century that small populations of closely related plants or animals are likely to suffer from low reproductive success, the exact mechanism by which this "inbreeding depression" occurs is still the subject of debate.

The new study, in Conservation Biology, is the first to look at inbreeding depression as it relates to the expression of all of an organism's genes to see which are more or less active in inbred populations and what they do.

By mating male and female fruit flies that were genetically identical to one another, researchers at the University of Illinois were able to determine how much the flies' genetic likeness reduced their reproductive success. They repeated the experiment in six lines of fruit flies that were identical to one another except for the composition of one of their chromosomes; only the genes of chromosome three differed between the lines.

The researchers also crossed the three highest inbred lines to one another, creating outbred lines that could be compared with the inbred ones.

Using oligonucleotide microarrays, which can measure the activity of all of an organism's genes at once, the researchers were able to see which genes were more or less active (up-regulated or down-regulated) in the inbred versus the outbred lines.

The six inbred lines of fruit flies showed a lot of variation in the degree of inbreeding depression, from 24 to 79 percent when compared with non-inbred flies. The researchers also found that 567 genes in the high inbreeding depression lines were expressed at higher or lower levels than the same genes in the other inbred lines. Only 62 percent of these genes were located on chromosome three (the only chromosome that differed between the lines) indicating that variation in chromosome t
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