Along with their collaborators at Agilent, the team designed ways to examine these newly identified sequences in a panel of people representing populations from around the world. The researchers found that, in some cases, the number of copies of these sequences varied from person to person.
The fact that a person can have one or more copies, or no copy at all, of a particular DNA sequence may account for why these sequences were missing from the reference genome. The researchers also found that some of these sequences were common or rare in different populations, depending on from which part of the globe their ancestors originated.
"Each segment of the reference genome is from a single person, and reflects the genome of that individual. If the donor sample was missing a sequence that many other people have, that sequence would not be represented in the reference genome." Kidd explained. "That is why some of the positions on the reference genome represent rare structural configurations or entirely omit sequences found in the majority of people." Kidd said that the study published in Nature Methods used information from nine individuals, representing various world populations, to search for and fill in some of the missing pieces.
By looking at genomes from seven kinds of animals, the researchers were also able to show that some of the newly identified DNA sequences appear to have been conserved during the evolution of mammals and man. The animals whose genomes were studied were chimpanzee, Bornean orangutan, Rhesus monkey, house mouse, Norway rat, dog, and horse.
"Some of the sequences were present in several different species, but were absent from the reference genome," Kidd said. "Some of the sequences present in several mammals actually correspond to sites of variations in humans some people have retained a particular sequence, and others have lost it."
The researchers also developed a method to accurately
|Contact: Leila Gray|
University of Washington