genetics

Chickens are unlikely harbingers of the invention of time travel, but a recent study using a line of White Plymouth Rock foul developed in Virginia Tech’s College of Agriculture and Life Sciences caused evolutionary history to speed up a bit.

Specifically, the experiment proved that evolution happens 15 times faster than previously thought.

The research was published recently in Biology Letters, a journal of Royal Society Publishing. The discovery involved researchers from several universities, including the University of York, Oxford University, the University of Sydney, Uppsala University, the Swedish University of Agricultural Sciences, and Virginia Tech.

“This experiment and many others involving everything from animal appetites to genetics could never have been done without the pedigree lines here at Virginia Tech,” said Siegel, distinguished professor emeritus of animal and poultry sciences in the College of Agriculture and Life Sciences. “This experiment was also an excellent example of international collaboration between six countries that was necessary for the success of the study.”

Siegel’s other primary research area using genetic lines of chickens focuses on why some animals pack on pounds and others don’t, and will be a key component of finding out how to breed chickens to feed the projected 9 billion people set to besiege the planet in 2050.

Siegel, along with Ben Dorshorst and Christa Honaker, also in the Virginia Tech Department of Animal and Poultry Sciences, were co-authors on the current paper.

The pedigree lines of White Plymouth Rock chickens were developed by Siegel, who began breeding them in 1957. From the common founder population, he produced two distinct lines of chickens selected for high- and low-body weight. Today, the high-weight line dwarfs its low-growth counterpart by an average of 12 times more by the time they reach the eight-week selection age.

In the latest experiment, researchers analyzed blood samples of chickens of the same generation using the most distantly related maternal lines to reconstruct how the mitochondrial DNA passed from mothers to daughters.

Mitochondria are specialized structures in the cells of animals, plants, and fungi that generate energy, synthesize proteins, and package proteins for transport to different parts of the cell and beyond.

Previously, estimates put the rate of change in a mitochondrial genome about 2 percent per million years,” Greger Larson, professor of archaeology at Oxford University, said in a news release. “At this pace we should not have been able to spot a single mutation in just 50 years, but in fact we spotted two.”

The sampling scheme yielded 385 mitochondrial transmissions that were analyzed for linkages within the mitochondrial DNA.

The rate of evolution was calculated by analyzing the number of observed mutations in the approximately 16,000 samples of mitochondrial DNA in the genome over 47 generations.

The scientists then reconstructed the maternal pedigree based on the mitogenome sequences.

“Our observations reveal that evolution is always moving quickly, but we tend not to see it because we typically measure it over longer time periods,” Larson said in the news release. “Our study shows that evolution can move much faster in the short term than we had believed from fossil-based estimates.”

The experiment also determined that mitochondria are not solely passed down from maternal lines. Strictly maternal inheritance has long been thought of as the characteristic of mitochondrial genomes.

“The thing everyone knew about mitochondria is that it is almost exclusively passed down the maternal line, but we identified chicks who inherited their mitochondria from their father,” said Michelle Alexander, lead author. This finding supports the theory that “paternal leakage” is not such a rare phenomenon.