Scientists have invented methods to scout the human genome's repetitive landscapes, where DNA sequences are highly identical and heavily duplicated. These advances, as reported today in Science, can identify subtle but important differences among people in the number and content of repeated DNA segments.
These copy number variations partly account for the normal diversity among people. Copy number variations might also be why some people, and not others, have certain disorders or disease susceptibilities, and might also determine how severely they are affected.
Until about a year ago, locating and counting the number of duplicated copies of DNA sequences was almost impossible. The more copies of a duplicated gene that are present, the harder they are to assess accurately.
"These difficulties resulted in a lack of understanding of the true extent of human copy number variation, " said Dr. Evan E. Eichler, University of Washington (UW) professor of genome sciences and senior author of the Science paper, "The most dynamic and variable genes are frequently excluded from genome-wide studies." These hard-to-study genes are also among the most interesting because of their suspected contributions to human evolution, brain development, metabolism and disease immunity.
Researchers in Eichler's lab have developed several analytical and computational techniques to overcome obstacles in looking at multicopy genes. The lead authors of the study are Peter H. Sudmant and Jacob O. Kitzman, both graduate students in the UW Department of Genome Sciences.
Working with colleagues in the 1000 Genomes Project and at Agilent Technologies, the UW group used the new techniques to deeply probe and compare the genomes of 159 individuals. In assessing the entire genomes of these individuals, the researchers were able to accurately assay previously intractable duplicated genes and gene families.
The researchers demo
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University of Washington