"These results suggest that a significant amount of inbreeding depression is due to a few key genes that affect the expression of other genes," said animal biology professor and department head Ken Paige, who led the study.
Of particular note were identical changes in the expression of 46 genes in all three of the high inbreeding depression lines, Paige said, making them of interest for further study.
Genes associated with inbreeding depression could be grouped into three broad categories of function: those involved in metabolism, stress, and defense. This is a surprising finding, Paige said, "because we think of inbreeding as a random process."
Many metabolic genes were up-regulated in the inbred flies, as were genes that fight pathogens such as bacteria or viruses. A third group of genes was down-regulated. They code for proteins that protect the body from reactive atoms and molecules that can damage cells.
These changes in gene expression are shunting energy away from reproduction and undermining some basic cellular functions, Paige said.
Inbreeding depression is thought to result from a deleterious pattern of inherited genes. In general, an organism with two parents has two versions of every gene one maternal and one paternal. These different flavors of a gene are called alleles. If the maternal and paternal alleles differ, one of them usually dominates, conferring all of its qualities to the offspring. The other, silenced allele is called "recessive."
Some alleles are detrimental to health. Most of these are recessive, meaning that they do not cause problems unless the organism inherits two copies of them one from each parent. When the alleles differ, one (the dominant allele) often masks the deleterious effects of the other.
But the interaction of parental alleles in their offspring can be quite complex. Sometimes an allele cause
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University of Illinois at Urbana-Champaign