Origins of genome complexity studied

ATLANTA, Dec. 15 (UPI) -- Georgia Tech biologists are supporting a controversial theory that has divided the fields of evolutionary genomics and developmental biology for two years.

Researchers say the size and complexity of a species' genome is not an evolutionary adaptation, but can result from a reduction in a species' effective population size.

"As a general rule, more complex organisms, like humans, have larger genomes than less complex ones," said Professor J. Todd Streelman, co-author of the study, but he says that's not always true.

"We see a very strong negative linear relationship between genome size and effective population size," said Professor Soojin Yi, the study's lead author. "This observation tells us the mutations that increase the genome tend to be slightly deleterious, because population genetic theories predict such a relationship.

"The interesting thing here is biological complexity may passively evolve," said Yi. "We show that at the origins, it's not adaptive mutations, but slightly bad ones, that make the genome larger. ... At first, maybe these mutations aren't so good for your genome, but as they accumulate and conditions change through evolution, they could become more complex and more beneficial."

The study appears in Trends in Genetics.