The nucleotide composition of genomes undergoes dramatic variations among all three kingdoms of life. GC
content, an important characteristic for a genome, is related to many important functions, and therefore GC content and its
distribution are routinely reported for sequenced genomes. Traditionally, GC content distribution is assessed by computing
GC contents in windows that slide along the genome. Disadvantages of this routinely used window-based method include
low resolution and low sensitivity. Additionally, different window sizes result in different GC content distribution
patterns within the same genome. We proposed a windowless method, the GC profile, for displaying GC content variations
across the genome. Compared to the window-based method, the GC profile has the following advantages: 1) higher
sensitivity, because of variation-amplifying procedures; 2) higher resolution, because boundaries between domains can be
determined at one single base pair; 3) uniqueness, because the GC profile is unique for a given genome and 4) the capacity
to show both global and regional GC content distributions. These characteristics are useful in identifying horizontallytransferred
genomic islands and homogenous GC-content domains. Here, we review the applications of the GC profile in
identifying genomic islands and genome segmentation points, and in serving as a platform to integrate with other algorithms
for genome analysis. A web server generating GC profiles and implementing relevant genome segmentation algorithms
is available at: www.zcurve.net.
Center for Molecular Medicine and Genetics, School of Medicine, Wayne State University, Detroit, MI, USA.