COLUMBUS, Ohio – An international team of scientists has sequenced the genome of the bonobo, a primate that, along with chimpanzees, is the closest living relative of humans. Unlike chimpanzees, which have an aggressive nature, bonobos tend to be peaceful, playful and highly sexual.

The study, published online in the journal Nature, compares the bonobo genome to the genomes of chimpanzees and humans.

As part of the study, scientists at the Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute (OSUCCC – James) analyzed and compared movable pieces of DNA called transposons in the three genomes.

"The findings will help scientists understand the evolutionary relationships between humans, chimpanzees and bonobos, and should help us learn more about the genetic basis for traits that humans share with these close relatives," says Dr. David E. Symer, assistant professor of molecular virology, immunology and medical genetics and leader of the Ohio State team. Symer worked closely with Dr. Keiko Akagi, a bioinformatics expert at Ohio State, and Saneyuki Higashino, a graduate student visiting from Japan.

Researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, led the study. They worked in collaboration with investigators at Aarhus University in Denmark, the University of Washington in Seattle, the National Human Genome Research Institute, The Ohio State University and other centers.

The team sequenced and assembled the genome of a female bonobo named Ulindi that lives in the Leipzig zoo.

They found that more than 3 percent of the human genome is more closely related to either the bonobo or the chimpanzee than the two apes are to each other, which indicates that the three species share a complex evolutionary relationship.

Transposons are popularly called "jumping genes" because they can move from one chromosomal location to another. They have accumulated in the genomes over evolutionary time and make up about half the genomic DNA of all three primates.

The Ohio State investigators identified the presence of more than 2.5 million transposons at identical locations in the chromosomes of all three species. They also found roughly 1,500 transposon insertions that are unique to the bonobo genome; that is, they are not present at the same genomic positions in the human or chimpanzee genomes, Symer says.

"These particular transposons inserted into the bonobo genome after they diverged from chimpanzees about a million years ago. They may be responsible for some of the key differences between bonobos, chimpanzees and humans, so we are continuing to study them," Symer says.