Chromosome breakpoints contribute to genetic...( CHAMPAIGN Ill. A new study reveals ...)

CHAMPAIGN, Ill. A new study reveals that contrary to decades of evolutionary thought chromosome regions that are prone to breakage when new species are formed are a rich source of genetic variation.

The functions of genes found in these "breakpoint regions" differ significantly from those occurring elsewhere in the chromosomes. This suggests that chromosomal organization plays an important evolutionary role, the researchers report.

The study, published in the journal Genome Research, is the first to show that different parts of chromosomes can have very different evolutionary histories, said University of Illinois animal sciences professor Harris Lewin, who led the research. Lewin directs the Institute for Genomic Biology and is part of an international team that sequenced the cow genome.

"Our results demonstrate that chromosome breakage in evolution is non-random and that the breakpoint regions and the more stable regions of chromosomes are evolving in distinctly different ways," he said.

When egg or sperm cells form in animals, maternal and paternal chromosomes first pair up and then recombine. The chromosomes literally break and reattach to one another. In most cases, the new chromosomes have the same arrangement of genes as the parent cells, but with new combinations of maternal and paternal genes.

The "crossing over" of segments of maternal and paternal chromosomes to form hybrid chromosomes has long been acknowledged as a driver of genetic variation.

Sometimes, however, the wrong chromosomes recombine, segments of chromosomes become inverted or complete breakages and fissions occur. These rearrangements may lead to genetic diseases or may contribute to the development of new species.

Until now, scientists have been unable to determine how the organization of genes along chromosomes and variatio
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