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Genetics is a crapshoot. During sexual reproduction, genes from both the mother and the father mix and mingle to produce a genetic combination unique to each offspring. In most cases, the chromosomes line up properly and crossover. In some unlucky cases, however, "selfish DNA" enters the mix, causing abnormal crossovers with deletions or insertions in chromosomes, which can manifest as birth defects.
Scientists have long recognized that the exchange of genetic material by crossing over—known as recombination—is vital to natural selection. Yet some species display far more crossover than others. Why? Researchers hypothesize that crossover rates have evolved to balance the benefits of crossing over with the risks of selfish DNA.
Bit - Mystery - Phenomena - Response - Elements
"There's a bit of a mystery being solved now about how certain molecular, biological, and genome phenomena have evolved in response to selfish genetic elements," says Daven Presgraves, a dean's professor of biology at the University of Rochester. "The role of natural selection in an ecological context is essentially a solved problem, but the role of natural selection in response to selfish genetic elements is still being worked out."
Presgraves and Ph.D. candidate Cara Brand recently accomplished an important milestone in learning about these evolutionary dynamics. By studying two species of fruit flies, they discovered a gene, MEI-218, that controls the rate of recombination. In a paper published in Current Biology, they explain how MEI-218 controls differences in the rate of crossing over between species and the evolutionary forces at play.
Gene - Anyone - Evolution - Recombination - Rates
"This is the first gene I know of that anyone has shown to be responsible for the evolution of recombination rates," Presgraves says.
The team focused on two closely related species of fruit flies—Drosophila melanogaster and its sister species, Drosophila mauritiana—because large differences have evolved in their rates of recombination: D. mauritiana does about 1.5 times more crossing over than D. melanogaster. When...
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