Researchers have found that large regions of the human genome may be duplicated or missing in individuals, and that these regions often overlap with gene-coding regions. This has important consequences as previously it was thought that most human variation was in "small-scale" mutations that affected single or a few nucleotides. But, the researchers have now found that these new variations "involve gains or losses of several kilobases to hundreds of kilobases of genomic DNA among phenotypically normal individuals."
Nature Genetics, Published online: 01 August 2004; doi:10.1038/ng1416
Detection of large-scale variation in the human genome
A John Iafrate et al.
We identified 255 loci across the human genome that contain genomic imbalances among unrelated individuals. Twenty-four variants are present in > 10% of the individuals that we examined. Half of these regions overlap with genes, and many coincide with segmental duplications or gaps in the human genome assembly. This previously unappreciated heterogeneity may underlie certain human phenotypic variation and susceptibility to disease and argues for a more dynamic human genome structure.